Golf balls having multi-layered covers made from plasticized compositions containing non-acid polymers

ABSTRACT

Multi-layered golf balls containing a three-layered cover assembly are provided. For example, a cover assembly having an inner cover, intermediate cover, and outer cover layer may be prepared. At least one of the cover layers is formed from a thermoplastic composition that preferably comprises: a) thermoplastic non-acid polymer, and b) plasticizer. A fatty acid ester such as ethyl oleate is preferably used as the plasticizer. Suitable non-acid polymers include, for example, polyesters, polyamides, polyolefins, and polyurethanes. The cover assembly has good impact durability and helps provide the ball with relatively high resiliency at given compressions.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of co-pending, co-assigned U.S. patentapplication Ser. No. 14/873,392 having a filing date of Oct. 2, 2015,now allowed, the disclosure of which is hereby incorporated byreference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates generally to multi-piece golf balls havinga solid core and multi-layered cover. In one embodiment, themulti-layered cover is a three-layered cover including an inner cover,intermediate cover, and outer cover layer. At least one of the coverlayers is made from a thermoplastic composition preferably comprising anon-acid polymer and plasticizer. Suitable non-acid polymers include,for example, polyesters, polyamides, polyolefins, and polyurethanes.Preferably, the plasticized thermoplastic composition is used to formthe intermediate or inner cover layer.

Brief Review of the Related Art

Multi-layered, solid golf balls are used today by recreational andprofessional golfers. In general, these golf balls contain an inner coreprotected by a cover. The core acts as the primary engine for the balland the cover protects the core and helps provide the ball withdurability and wear-resistance. The core and cover may be single ormulti-layered. For example, three-piece golf balls having an inner core,inner cover layer, and outer cover layer are popular. In otherinstances, golfers will use a four-piece ball containing a dual-core(inner core and surrounding outer-core layer) and dual-cover (innercover layer and surrounding outer cover layer). Intermediate layer(s)may be disposed between the core and cover layers to impart variousproperties. Thus, five-piece and even six-piece balls can be made.

Normally, the core layers are made of a natural or synthetic rubbermaterial or an acid copolymer ionomer. These ionomer polymers aretypically copolymers of ethylene and methacrylic acid or acrylic acidthat are partially or fully-neutralized. Metal ions such as sodium,lithium, zinc, and magnesium are commonly used to neutralize the acidgroups in the copolymer. The acid groups may be partially-neutralized(where typically, about 10 to 70% of the acid groups are neutralized) orhighly-neutralized (where typically, greater than 70% of the acid groupsare neutralized.) In addition to being used as a core material, theseacid copolymer ionomers may be used to make intermediate and coverlayers for the golf ball. Such ionomer resins generally have gooddurability and toughness. When used as a core material, the ionomerresin helps impart a higher initial velocity to the golf ball. When usedas a cover material, the ionomer resin helps impart impact durability,wear-resistance, and cut/shear-resistance to the golf ball.

Many golf balls have multi-layered covers comprising an inner cover andsurrounding outer cover layer. For example, the inner cover may be madeof a relatively hard material such as the above-described ethylene acidcopolymer ionomer resin. Meanwhile, the outer cover layer may be made ofa relatively soft polyurethane or polyurethane composition. Also,three-layered covers, wherein the cover structure includes an innercover, intermediate cover, and outer cover layer may be made. The patentliterature describes numerous golf ball covers made from such ethyleneacid copolymer ionomer compositions including, for example, U.S. Pat.Nos. 5,688,869; 6,150,470; 6,277,921; 6,433,094; 6,451,923; 6,573,335;and 6,800,695.

However, one disadvantageous feature of such ionomer cover balls is theytend to have a hard “feel.” Some players experience a harsher, lesscomfortable feel when their club face makes contact with these hardballs. The player senses less control and the harder ball tends to havelow initial spin. It is generally more difficult to hit hard balls withthe proper touch and control. This can be particularly troublesome whenmaking approach shots with irons near the green.

Thus, the industry has looked at numerous non-ionomeric materials suchas polyolefins, polyamides, polyesters, polyurethanes, polyureas,fluoropolymers, polyvinyl chlorides, polycarbonates, polyethers,polyimides, and the like for making components and layers in golf balls.For example, Sullivan et al., U.S. Pat. No. 6,872,774 discloses amulti-layered golf ball having a core, intermediate layer, and cover.The intermediate layer is made of a composition comprising anon-ionomeric acid polymer and non-ionomeric stiffening polymerincluding blends of polyamides and polypropylene and polyethylenecopolymers that have been grafted with maleic anhydride or sulfonategroups.

In Rajagopalan et al., U.S. Pat. No. 6,800,690 golf balls having atleast one layer formed from a composition comprising a polyamide andnon-ionomeric material including grafted or non-graftedmetallocene-catalyzed olefinic polymers such as polyethylene andcopolymers of ethylene are disclosed. The olefinic polymers may alsocontain functional groups such as epoxy, anhydride, amine, oxazoline,sulfonic acid, carboxylic acid, and their salts.

Kim et al, US Patent Application Publication US 2010/0167845 disclosesgolf balls having a core, at least one intermediate layer, and at leastone cover layer prepared from blends of polyamides with functionalpolymer modifiers of the polyamide. The functional modifier of thepolyamide can include ∝-olefin copolymers or terpolymers having aglycidyl group, hydroxyl group, maleic anhydride group, or carboxylicgroup. The polyamide composition is preferably blended with apolyalkenamer rubber/functionalized organic modifier material.

In Loper et al., US Patent Application Publication 2006/0172823,four-piece golf balls having one or more core layers, an inner mantlelayer, an outer mantle layer, and one or more cover layers aredisclosed. In one embodiment, the composition of inner mantle layerand/or the outer mantle layer comprises a blend of polyamide orcopolymeric polyamide and another polymer. According to the '823Publication, suitable other polymers for the blend include ionomers,co-polyetheramide elastomers, polyarylates, polyolefins, polyoctenamers,polyurethanes, styrenic block copolymers, metallocene catalizedpolymers, and polyesters.

Although some non-ionomeric compositions as mentioned above may besomewhat effective for making certain components and layers in a golfball, there is still a need for new compositions that can impart highquality performance properties to the ball. Particularly, there is acontinuing need for improved cover constructions in golf balls. Thecover material should have good impact durability, toughness, andcut/shear-resistance, while helping to provide the ball with highresiliency. The cover material, however, should not be excessively hardand stiff so that properties such as feel, softness, and spin controlare sacrificed. The present invention provides golf balls having anoptimum combination of properties.

SUMMARY OF THE INVENTION

The present invention generally relates to multi-layered golf balls andmore particularly to golf balls having at least one layer made ofthermoplastic non-acid polymer/plasticizer compositions. In one version,the ball comprises a core having at least one layer and a three-layeredcover assembly including: a) an inner cover comprising a thermoplasticmaterial, b) an intermediate cover disposed about the inner cover layer,and c) a surrounding outer cover. Preferably, the thermoplastic materialcomprises: i) a thermoplastic non-acid polymer and ii) a plasticizer. Inone embodiment, the inner cover layer has a Shore D midpoint hardness inthe range of about 15 to about 60 Shore D, and the outer cover layer hasShore D surface hardness in the range of about 45 to about 75 Shore D,wherein the hardness of the outer cover layer is greater than thehardness of the inner cover layer.

Various non-acid polymers may be used in the thermoplastic composition.For example, non-acid polymers selected from the group consisting offluoropolymers, polystyrenes, polyolefins, polyamides, polyesters,polyethers, polyurethanes, polyureas, polyvinyl chlorides, polyvinylacetates, polyimides, ethylene propylene rubber, ethylene propylenediene rubber, styrenic block copolymer rubbers, alkyl acrylate rubbers,and mixtures thereof may be used. In one preferred version, a polyamideselected from the group consisting of polyamide 6; polyamide 6,6;polyamide 6,10; polyamide 6,12; polyamide 11; polyamide 12; polyamide6,9; and polyamide 4,6, and copolymers and blends thereof is used. Inanother version, the non-acid polymer is selected from the groupconsisting of a polyether-amide block copolymer and apolyester-polyether block copolymer, and mixtures thereof. Variousplasticizers may be used in the thermoplastic composition. In oneparticularly preferred version, the thermoplastic composition comprisesa fatty acid ester, particularly an alkyl oleate, and more particularlyethyl oleate. Preferably, the thermoplastic composition comprises about3 to about 50% by weight plasticizer, more preferably about 8 to about42%, and even more preferably about 10 to about 30%, plasticizer basedon weight of composition. Various materials may be used to form theintermediate and outer cover layers. In one preferred embodiment, theintermediate cover layer comprises a second thermoplastic material andthe outer cover layer comprises a third thermoplastic material. Acidcopolymer ionomers and polyurethanes/polyureas may be used as the secondand third thermoplastic cover layers.

In a second embodiment, the ball comprises a core having at least onelayer and a three-layered cover assembly including an inner cover; anintermediate cover layer comprising a thermoplastic composition,preferably comprising: i) a thermoplastic non-acid polymer and ii) aplasticizer; and a surrounding outer cover layer. The inner cover layerpreferably has a Shore D midpoint hardness in the range of about 15 toabout 75 Shore D, and the outer cover layer has Shore D surface hardnessin the range of about 45 to about 75 Shore D, wherein the hardness ofthe outer cover layer is greater than the hardness of the inner cover.

In a third embodiment, the ball comprises a core having at least onelayer and a three-layered cover assembly including an inner cover; anintermediate cover layer disposed about the inner cover; and an outercover layer comprising a thermoplastic composition, preferablycomprising: i) a thermoplastic non-acid polymer and ii) a plasticizer.The inner and intermediate cover layers preferably each have a hardnessgreater than the hardness of the outer cover layer.

The thermoplastic non-acid polymer/plasticizer compositions of thisinvention may be used to form one or more core, intermediate, or coverlayers. These compositions have a good combination of propertiesincluding Coefficient of Restitution (CoR) and compression so they canbe used to make various golf ball layers. For example, a molded spherecomprising the thermoplastic composition of this invention having aCoefficient of Restitution of at least about 0.750, preferably at leastabout 0.800; and a Shore C surface hardness of about 10 to about 75,preferably about 20 to about 60 can be made. In one embodiment, ballshaving a relatively low compression, for example, in the range of about25 to about 75, may be made.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features that are characteristic of the present invention areset forth in the appended claims. However, the preferred embodiments ofthe invention, together with further objects and attendant advantages,are best understood by reference to the following detailed descriptionin connection with the accompanying drawings in which:

FIG. 1 is a perspective view of a dimpled golf ball made in accordancewith the present invention;

FIG. 2 is a cross-sectional view of a four-piece golf ball having a coreand multi-layered cover made in accordance with the present invention;

FIG. 3 is a cross-sectional view of a five-piece golf ball having adual-core and multi-layered cover made in accordance with the presentinvention; and

FIG. 4 is a cross-sectional view of a six-piece golf ball having adual-core; an intermediate layer; and multi-layered cover made inaccordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Golf Ball Constructions

Golf balls having various constructions may be made in accordance withthis invention. For example, golf balls having one-piece, two-piece,three-piece, four-piece, and five or more-piece constructions with theterm “piece” referring to any core, cover or intermediate layer of agolf ball construction. Representative illustrations of such golf ballconstructions are provided and discussed further below. The term,“layer” as used herein means generally any spherical portion of the golfball. More particularly, in one version, a one-piece ball is made usingthe inventive composition as the entire golf ball excluding any paint orcoating and indicia applied thereon. In a second version, a two-pieceball comprising a single core and a single cover layer is made. In athird version, a three-piece golf ball containing a dual-layered coreand single-layered cover is made. The dual-core includes an inner core(center) and surrounding outer core layer. In another version, athree-piece ball containing a single core layer and two cover layers ismade. In yet another version, a four-piece golf ball containing adual-core and dual-cover (inner cover and outer cover layers) is made.In yet another construction, a four-piece golf ball containing a core;an inner cover layer, an intermediate cover layer, and an outer coverlayer, may be made. In still another construction, a five-piece ball ismade containing an a dual-core, an inner cover layer, an intermediatecover layer, and an outer cover layer. The diameter and thickness of thedifferent layers along with properties such as hardness and compressionmay vary depending upon the construction and desired playing performanceproperties of the golf ball. Any one or more of the layers of any of theone, two, three, four, or five, or more-piece (layered) balls describedabove may comprise a plasticized thermoplastic composition as disclosedherein. That is, any of the inner (center) core and/or outer corelayers, and/or inner, intermediate, or outer cover layers may comprise aplasticized composition of this invention.

Also, when more than one thermoplastic layer is used in the golf ball,the thermoplastic composition in the respective layers may be the sameor different, and the composition may have the same or differenthardness values. For example, a three-layered cover assembly may bemade, wherein the inner cover comprises a first thermoplasticcomposition, the intermediate cover layer comprises a secondthermoplastic composition, and the outer cover layer comprises a thirdthermoplastic composition. The first, second, and third compositions maybe the same, or the respective compositions may be different. Forinstance, the plasticized thermoplastic of this invention may be used inone, two, or three cover layers. Preferably, the plasticizedthermoplastic composition of this invention is used to form at least onecover layer. Likewise, when more than one thermoset layer is used in thegolf ball, the thermoset composition in the respective layers may be thesame or different, and the composition may have the same or differenthardness values. Furthermore, in some examples, the thermoplasticmaterial in a particular thermoplastic layer may constitute two, three,or more “sub-layers” of the same or different thermoplastic composition.That is, each thermoplastic layer can be formed from one or moresub-layers of the same or different thermoplastic material. In suchinstances, the thermoplastic layer can be considered a composite layermade of multiple independent and distinct component layers. Preferably,at least one of the component layers comprises the plasticizedthermoplastic composition of this invention.

Non-Acid Polymers

Non-acid polymer compositions (NAPS), which are plasticized per thisinvention, may be used to form any layer in the golf ball constructionsof this invention. The term, “non-acid polymer,” as used herein, means apolymer which is not an “acid polymer”—in general, by the term, “acidpolymer”, it is meant a polymer containing free carboxylic acid groupsthat is formed from free carboxylic acid-containing monomers. The term,“polymer” is used generically herein to refer to a large molecule(macromolecule) having repeating structural units typically connected bycovalent bonds and includes, but is not limited to, oligomers,homopolymers, copolymers, and mixtures thereof. The term, “copolymer,”as used herein, includes polymers formed from two, three, or moredifferent types of monomers. It is understood the non-acid polymercompositions of this invention may contain a blend of two or morenon-acid polymers.

Suitable non-acid polymers that may be used to form the compositions ofthis invention include, but are not limited to, the following: a)polyesters and particularly plasticized polyester compositions such asthose described in co-pending, co-assigned U.S. patent application Ser.No. 14/532,141, the disclosure of which is hereby incorporated byreference; b) polyamides, and particularly plasticized polyamidecompositions such as those described in co-pending, co-assigned U.S.patent application Ser. No. 14/309,066 (Publication US 2014/0302947),Ser. No. 14/330,189 (Publication US 2014/0323243), and Ser. No.14/563,646, the disclosures of which are hereby incorporated byreference; and c) polyurethanes, polyureas, and polyurethane-polyureahybrids and particularly plasticized polyurethane compositions such asthose described in in co-pending, co-assigned U.S. patent applicationSer. No. 14/672,485, the disclosure of which is hereby incorporated byreference.

Other examples of non-acid polymers include fluoropolymers;metallocene-catalyzed polymers; polystyrenes,acrylonitrile-butadiene-styrene, poly(styrene sulfonate), polyethylenestyrene: polyolefins such as polypropylenes and polyethylenes, andparticularly grafted polypropylenes and grafted polyethylenes that aremodified with a functional group, such as maleic anhydride of sulfonate;polyvinyl chlorides and grafted polyvinyl chlorides; polyvinyl acetates;polycarbonates; polyethers, such as polyarylene ethers, polyphenyleneoxides; polyimides; polyetherketones; and polyamideimides. Inparticular, the non-acid polymer was not polymerized from any of thefollowing monomers containing free carboxylic acid groups: acrylic acid,methacrylic acid, ethacrylic acid, maleic acid, crotonic acid, fumaricacid, and itaconic acid.

Examples of particularly suitable commercially available non-acidpolymers include, but are not limited to, Lotader® ethylene-alkylacrylate polymers and Lotryl® ethylene-alkyl acrylate polymers, andparticularly Lotader® 4210, 4603, 4700, 4720, 6200, 8200, and AX8900commercially available from Arkema Corporation; Elvaloy® ACethylene-alkyl acrylate polymers, and particularly AC 1224, AC 1335, AC2116, AC3117, AC3427, and AC34035, commercially available from E. I. duPont de Nemours and Company; Fusabond® elastomeric polymers, such asethylene vinyl acetates, polyethylenes, metallocene-catalyzedpolyethylenes, ethylene propylene rubbers, and polypropylenes, andparticularly Fusabond® N525, C190, C250, A560, N416, N493, N614, P614,M603, E100, E158, E226, E265, E528, and E589, commercially availablefrom E. I. du Pont de Nemours and Company; Honeywell A-C polyethylenesand oxidized polyethylenes such as A-C 655, and A-C 395, commerciallyavailable from Honeywell; Nordel® IP rubber, Elite® polyethylenes,Engage® elastomers, and Amplify® functional polymers, and particularlyAmplify® GR 207, GR 208, GR 209, GR 213, GR 216, GR 320, GR 380, and EA100, commercially available from The Dow Chemical Company; Enable®metallocene polyethylenes, Exact® plastomers, Vistamaxx® propylene-basedelastomers, and Vistalon® EPDM rubber, commercially available fromExxonMobil Chemical Company; Starflex® metallocene linear low densitypolyethylene, commercially available from LyondellBasell; Elvaloy®HP4051, HP441, HP661 and HP662 ethylene-butyl acrylate-carbon monoxidepolymers and Elvaloy® 741, 742 and 4924 ethylene-vinyl acetate-carbonmonoxide polymers, commercially available from E. I. du Pont de Nemoursand Company; Evatane® ethylene-vinyl acetate polymers having a vinylacetate content of from 18 to 42%, commercially available from ArkemaCorporation; Elvax® ethylene-vinyl acetate polymers having a vinylacetate content of from 7.5 to 40%, commercially available from E. I. duPont de Nemours and Company; Vamac® G terpolymer of ethylene,methylacrylate and a cure site monomer, commercially available from E.I. du Pont de Nemours and Company; Vistalon® EPDM rubbers, commerciallyavailable from ExxonMobil Chemical Company; Kraton® styrenic blockcopolymers, and particularly Kraton® FG1901GT, FG1924GT, and RP6670GT,commercially available from Kraton Performance Polymers Inc.; Septon®styrenic block copolymers, commercially available from Kuraray Co.,Ltd.; Hytrel® polyester elastomers, and particularly Hytrel® 3078, 4069,and 5556, commercially available from E. I. du Pont de Nemours andCompany; Riteflex® polyester elastomers, commercially available fromCelanese Corporation; Pebax® thermoplastic polyether block amides, andparticularly Pebax® 2533, 3533, 4033, and 5533, commercially availablefrom Arkema Inc.; Affinity® and Affinity® GA elastomers, Versify®ethylene-propylene copolymer elastomers, and Infuse® olefin blockcopolymers, commercially available from The Dow Chemical Company;Exxelor® polymer resins, and particularly Exxelor® PE 1040, PO 1015, PO1020, VA 1202, VA 1801, VA 1803, and VA 1840, commercially availablefrom ExxonMobil Chemical Company; and Royaltuf® EPDM, and particularlyRoyaltuf®498 maleic anhydride modified polyolefin based on an amorphousEPDM and Royaltuf®485 maleic anhydride modified polyolefin based on ansemi-crystalline EPDM, commercially available from Chemtura Corporation.

In particular, the non-acid polymer may be a non-acid elastomericpolymer such as, for example, ethylene-alkyl acrylate polymers,particularly polyethylene-butyl acrylate, polyethylene-methyl acrylate,and polyethylene-ethyl acrylate; metallocene-catalyzed polymers;ethylene-butyl acrylate-carbon monoxide polymers and ethylene-vinylacetate-carbon monoxide polymers; polyethylene-vinyl acetates;ethylene-alkyl acrylate polymers containing a cure site monomer;ethylene-propylene rubbers and ethylene-propylene-diene monomer rubbers;olefinic ethylene elastomers, particularly ethylene-octene polymers,ethylene-butene polymers, ethylene-propylene polymers, andethylene-hexene polymers; styrenic block copolymers; polyester andpolyamide elastomers; polyolefin rubbers, particularly polybutadiene,polyisoprene, and styrene-butadiene rubber; and thermoplasticpolyurethanes.

Additional examples of non-acid polymers that may be used to make thecompositions of this invention include, for example, natural andsynthetic rubbers, including, but not limited to, ethylene propylenerubber (“EPR”), ethylene propylene diene rubber (“EPDM”), styrenic blockcopolymer rubbers (such as SI, SIS, SB, SBS, SIBS, and the like, where“S” is styrene, “I” is isobutylene, and “B” is butadiene), butyl rubber,halobutyl rubber, copolymers of isobutylene and para-alkylstyrene,halogenated copolymers of isobutylene and para-alkylstyrene, naturalrubber, polyisoprene, copolymers of butadiene with acrylonitrile,polychloroprene, alkyl acrylate rubber (such as ethylene-alkyl acrylatesand ethylene-alkyl methacrylates, and, more specifically, ethylene-ethylacrylate, ethylene-methyl acrylate, and ethylene-butyl acrylate),chlorinated isoprene rubber, acrylonitrile chlorinated isoprene rubber,and polybutadiene rubber (cis and trans).

The non-acid polymers of this invention stand in contrast to acidpolymers and ionomers that are often used in golf ball constructions andare typically copolymers of an α-olefin and a C₃-C₈ α,β-ethylenicallyunsaturated carboxylic acid with an optional softening monomer. Theseacid copolymers are normally reacted with a sufficient amount of cationsource such that at least 70% and more typically at least 90% of allacid groups present are neutralized to form the ionomer.

Normally, an ionomer is made by polymerizing a monomer containing a freecarboxylic acid group and α-olefin; and neutralizing at least some ofthe acid groups with a metal cation. For example, ethylene andmethacrylic acid first may be reacted to form the acid polymer as shownin the following diagram:

Production of Acid Polymer

Then, the ionomer may be formed through neutralization by reacting theacid polymer with a cation source (for example, a sodium or zinc cationsource). For example, the acid polymer may be reacted with NaOH orZnCO₃. In one example, the resulting polymer is a sodium salt as shownin the following diagram:

Production of Ionomer

As described above, the non-acid polymers of this invention differsignificantly from the above-described acid polymers and correspondingionomers that are formed from such acid polymers, because the non-acidpolymers of this invention are not formed from free carboxylicacid-containing monomers and these polymers do not contain freecarboxylic acid groups.

Plasticizers for Making Thermoplastic Compositions

As discussed above, the non-acid polymer compositions of this inventioncontain a plasticizer. Adding the plasticizers helps to reduce the glasstransition temperature (Tg) of the composition. The glass transition ina polymer is a temperature range below which a polymer is relativelybrittle and above which it is rubber-like. In addition to lowering theTg, the plasticizer may also reduce the tanδ in the temperature rangeabove the Tg. The Tg of a polymer is measured by a Differential Scanningcalorimeter or a Dynamic Mechanical Analyzer (DMA) and the DMA is usedto measure tanδ. The plasticizer may also reduce the hardness andcompression of the composition when compared to its non-plasticizedcondition. The effects of adding a plasticizer to the non-acid polymercomposition on Tg, flex modulus, hardness, and other physical propertiesare discussed further below.

The non-acid polymer composition may contain one or more plasticizers.The plasticizers that may be used in the non-acid polymer compositionsof this invention include, for example, N-butylbenzenesulfonamide(BBSA); N-ethylbenzenesulfonamide (EBSA); N-propylbenzenesulfonamide(PBSA); N-butyl-N-dodecylbenzenesulfonamide (BDBSA);N,N-dimethylbenzenesulfonamide (DMBSA); p-methylbenzenesulfonamide;o,p-toluene sulfonamide; p-toluene sulfonamide;2-ethylhexyl-4-hydroxybenzoate; hexadecyl-4-hydroxybenzoate;1-butyl-4-hydroxybenzoate; dioctyl phthalate; diisodecyl phthalate;di-(2-ethylhexyl) adipate; and tri-(2-ethylhexyl) phosphate; and blendsthereof.

In one preferred version, the plasticizer is selected from the group ofpolytetramethylene ether glycol (available from BASF under thetradename, PolyTHF™ 250); propylene carbonate (available from HuntsmanCorp., under the tradename, Jeffsol™ PC); and/or dipropyleneglycoldibenzoate (available from Eastman Chemical under the tradename,Benzoflex™ 284). Mixtures of these plasticizers also may be used.

Other suitable plasticizer compounds include benzene mono-, di-, andtricarboxylic acid esters. Phthalates such as Bis(2-ethylhexyl)phthalate (DEHP), Diisononyl phthalate (DINP), Di-n-butyl phthalate(DnBP, DBP), Butyl benzyl phthalate (BBP), Diisodecyl phthalate (DIDP),Dioctyl phthalate (DnOP), Diisooctyl phthalate (DIOP), Diethyl phthalate(DEP), Diisobutyl phthalate (DIBP), and Di-n-hexyl phthalate, and blendsthereof are suitable. Iso- and terephthalates such as Dioctylterephthalate and Dinonyl isophthalate may be used. Also appropriate aretrimellitates such as Trimethyl trimellitate (TMTM),Tri-(2-ethylhexyl)trimellitate (TOTM),Tri-(n-octyl,n-decyl) trimellitate,Tri-(heptyl,nonyl) trimellitate, Tri-n-octyl trimellitate; as well asbenzoates, including: 2-ethylhexyl-4-hydroxy benzoate, n-octyl benzoate,methyl benzoate, and ethyl benzoate, and blends thereof.

Also suitable are alkyl diacid esters commonly based on C4-C12 alkyldicarboxylic acids such as adipic, sebacic, azelaic, and maleic acidssuch as: Bis(2-ethylhexyl)adipate (DEHA), Dimethyl adipate (DMAD),Monomethyl adipate (MMAD), Dioctyl adipate (DOA), Dibutyl sebacate(DBS), Dibutyl maleate (DBM), Diisobutyl maleate (DIBM), Dioctylsebacate (DOS), and blends thereof. Also, esters based on glycols,polyglycols and polyhydric alcohols such as poly(ethylene glycol) mono-and di-esters, cyclohexanedimethanol esters, sorbitol derivatives; andtriethylene glycol dihexanoate, diethylene glycol di-2-ethylhexanoate,tetraethylene glycol diheptanoate, and ethylene glycol dioleate, andblends thereof may be used.

Fatty acids, fatty acid salts, fatty acid amides, and fatty acid estersalso may be used in the compositions of this invention. Compounds suchas stearic, oleic, ricinoleic, behenic, myristic, linoleic, palmitic,and lauric acid esters, salts, and mono- and bis-amides can be used.Ethyl oleate, butyl stearate, methyl acetylricinoleate, zinc oleate,ethylene bis-oleamide, and stearyl erucamide are suitable. Suitablefatty acid salts include, for example, metal stearates, erucates,laurates, oleates, palmitates, pelargonates, and the like. For example,fatty acid salts such as zinc stearate, calcium stearate, magnesiumstearate, barium stearate, and the like can be used. Fatty alcohols andacetylated fatty alcohols are also suitable, as are carbonate esterssuch as propylene carbonate and ethylene carbonate. Mixtures of any ofthe plasticizers described herein also may be used in accordance withthis invention. In a particularly preferred version, the fatty acidester is an alkyl oleate selected from the group consisting of methyl,propyl, ethyl, butyl, octyl, and decyl oleates. For example, in oneversion, ethyl oleate is used as the plasticizer. In another version,butyl oleate or octyl oleate is used in the composition. Suitablecommercially-available fatty acids include, for example, SylFat™ FA2Tall Fatty Acid, available from Arizona Chemical. The fatty acidcomposition includes 2% saturated, 50% oleic, 37% linoleic(non-conjugated), and 7% linoleic (conjugated) fatty acids; and 4% otherfatty acids. This fatty acid typically has an acid value in the range of195 to 205 mg KOH/gm.

Glycerol-based esters such as soy-bean, tung, or linseed oils or theirepoxidized derivatives or blends thereof can also be used asplasticizers in the present invention, as can polymeric polyesterplasticizers formed from the esterification reaction of diacids anddiglycols as well as from the ring-opening polymerization reaction ofcaprolactones with diacids or diglycols. Citrate esters and acetylatedcitrate esters are also suitable. Glycerol mono-, di-, and tri-oleatesmay be used per this invention, and in one preferred embodiment,glycerol trioleate is used as the plasticizer.

Dicarboxylic acid molecules containing both a carboxylic acid ester anda carboxylic acid salt can perform suitably as plasticizers. Themagnesium salt of mono-methyl adipate and the zinc salt of mono-octylglutarate are two such examples for this invention. Tri- andtetra-carboxylic acid esters and salts can also be used.

Also envisioned as suitable plasticizers are organophosphate andorganosulfur compounds such as tricresyl phosphate (TCP), tributylphosphate(TBP), octyldiphenyl phosphate, alkyl sulfonic acid phenylesters (ASE); and blends thereof; and sulfonamides such as N-ethyltoluene sulfonamide,N-(2-hydroxypropyl) benzene sulfonamide, N-(n-butyl)benzene sulfonamide. Furthermore, thioester and thioether variants ofthe plasticizer compounds mentioned above are suitable.

Non-ester plasticizers such as alcohols, polyhydric alcohols, glycols,polyglycols, and polyethers also are suitable materials forplasticization. Materials such as polytetramethylene ether glycol,poly(ethylene glycol), and poly(propylene glycol), oleyl alchohol, andcetyl alcohol can be used. Hydrocarbon compounds, both saturated andunsaturated, linear or cyclic can be used such as mineral oils,microcrystalline waxes, or low-molecular weight polybutadiene.Halogenated hydrocarbon compounds can also be used.

Other examples of plasticizers that may be used in the ethylene acidcopolymer composition of this invention include butylbenzenesulphonamide(BBSA), ethylhexyl para-hydroxybenzoate (EHPB) and decylhexylpara-hydroxybenzoate (DHPB), as disclosed in Montanari et al., U.S. Pat.No. 6,376,037, the disclosure of which is hereby incorporated byreference.

Esters and alkylamides such as phthalic acid esters including dimethylphthalate, diethyl phthalate, dibutyl phthalate, diheptyl phthalate,di-2-ethylhexyl phthalate, di-n-octyl phthalate, diisodecyl phthalate,ditridecyl phthalate, dicyclohexyl phthalate, butylbenzyl phthalate,diisononyl phthalate, ethylphthalylethyl glycolate, butylphthalylbutylglycolate, diundecyl phthalate, di-2-ethylhexyl tetrahydrophthalate asdisclosed in Isobe et al., U.S. Pat. No. 6,538,099, the disclosure ofwhich is hereby incorporated by reference, also may be used.

Jacques et al., U.S. Pat. No. 7,045,185, the disclosure of which ishereby incorporated by reference, discloses sulphonamides such asN-butylbenzenesulphonamide, ethyltoluene-suiphonamide,N-cyclohexyltoluenesulphonamide, 2-ethylhexyl-para-hydroxybenzoate,2-decylhexyl-para-hydroxybenzoate, oligoethyleneoxytetrahydrofurfurylalcohol, or oligoethyleneoxy malonate; esters of hydroxybenzoic acid;esters or ethers of tetrahydrofurfuryl alcohol, and esters of citricacid or hydroxymalonic acid; and these plasticizers also may be used.

Sulfonamides also may be used in the present invention, and thesematerials are described in Fish, Jr. et al., U.S. Pat. No. 7,297,737,the disclosure of which is hereby incorporated by reference. Examples ofsuch sulfonamides include N-alkyl benzenesulfonamides andtoluenesufonamides, particularly N-butylbenzenesulfonamide,N-(2-hydroxypropyl)benzenesulfonamide, N-ethyl-o-toluenesulfonamide,N-ethyl-p-toluenesulfonamide, o-toluenesulfonamide,p-toluenesulfonamide. Such sulfonamide plasticizers also are describedin Hochstetter et al., US Patent Application Publication 2010/0183837,the disclosure of which is hereby incorporated by reference.

As noted above, the fatty acid esters are particularly preferredplasticizers in the present invention. It has been found that the fattyacid esters perform well as plasticizers in the non-acid polymercomposition. The fatty acid esters have several advantageous properties.For example, the fatty acid esters are compatible with the non-acidpolymers and they tend to blend uniformly and completely with thenon-acid polymer. Also, the fatty acid esters tend to improve theresiliency and/or compression of the composition as discussed furtherbelow. The non-acid polymer/plasticizer compositions may contain otheringredients that do not materially affect the basic and novelcharacteristics of the composition. For example, mineral fillers may beadded as discussed above. In one particular version, the compositionconsists essentially of non-acid polymer and plasticizer, particularly afatty acid ester. In another particular version, the compositionconsists solely of non-acid polymer and plasticizer, particularly afatty acid ester.

One method of preparing the fatty acid ester involves reacting the fattyacid or mixture of fatty acids with a corresponding alcohol. Any alcoholcan be used including, but not limited to, linear, branched, and cyclicalcohols. The fatty acid ester is commonly a methyl, ethyl, propyl,butyl, octyl, or other alkyl ester of a carboxylic acid that containsfrom 4 to 30 carbon atoms. In the present invention, ethyl, butyl,octyl, and decyl esters and particularly ethyl oleate, butyl oleate, andoctyl oleate are preferred fatty acid esters because of theirproperties. The carboxylic acid may be saturated or unsaturated.Examples of suitable saturated carboxylic acids, that is, carboxylicacids in which the carbon atoms of the alkyl chain are connected bysingle bonds, include but are not limited to butyric acid (chain lengthof C₄ and molecular weight of 88.1); capric acid (C₁₀ and MW of 172.3);lauric acid (C₁₂ and MW of 200.3); myristic acid (C₁₄ and MW of 228.4);palmitic acid (C₁₆ and MW of 256.4); stearic acid (C₁₈ and MW of 284.5);and behenic acid (C₂₂ and MW of 340.6). Examples of suitable unsaturatedcarboxylic acids, that is, a carboxylic acid in which there is one ormore double bonds between the carbon atoms in the alkyl chain, includebut are not limited to oleic acid (chain length and unsaturation C18:1;and MW of 282.5); linoleic acid (C18:2 and MW of 280.5; linolenic acid(C18:3 and MW of 278.4); and erucic acid (C22:1 and MW of 338.6).

It is believed the plasticizer should be added in a sufficient amount tothe non-acid polymer composition so there is a substantial change in thestiffness and/or hardness of the non-acid polymer. Thus, although theconcentration of plasticizer may be as little as 1% by weight to formsome non-acid polymer compositions per this invention, it is preferredthat the concentration be relatively greater. For example, it ispreferred that the concentration of the plasticizer be at least 3 weightpercent (wt. %). More particularly, it is preferred that the plasticizerbe present in an amount within a range having a lower limit of 1% or 3%or 5% or 7% or 8% or 10% or 12% or 15% or 18% and an upper limit of 20%or 22% or 25% or 30% or 35% or 40% or 42% or 50% or 55% or 60% or 66% or71% or 75% or 80%. In one preferred embodiment, the concentration ofplasticizer falls within the range of about 7% to about 75%, preferablyabout 9% to about 55%, and more preferably about 15% to about 50%.

The plasticized compositions of the present invention, in the neat(i.e., unfilled) form, preferably have a specific gravity of 0.90 g/ccto 1.00 g/cc, more preferably 0.95 g/cc to 0.99 g/cc. Any suitablefiller, flake, fiber, particle, or the like, of an organic or inorganicmaterial may be added to the HNP composition to increase or decrease thespecific gravity, particularly to adjust the weight distribution withinthe golf ball, as further disclosed in U.S. Pat. Nos. 6,494,795,6,547,677, 6,743,123, 7,074,137, and 6,688,991, the entire disclosuresof which are hereby incorporated herein by reference. The term,“specific gravity” as used herein, has its ordinary and customarymeaning, that is, the ratio of the density of a substance to the densityof water at 4° C., and the density of water at this temperature is 1g/cm³.

The plasticized compositions of the present invention optionally includeadditive(s) and/or filler(s) in an amount within a range having a lowerlimit of 0 or 5 or 10 wt %, and an upper limit of 15 or 20 or 25 or 30or 50 wt %, based on the total weight of the composition. Suitableadditives and fillers include, but are not limited to, chemical blowingand foaming agents, optical brighteners, coloring agents, fluorescentagents, whitening agents, UV absorbers, light stabilizers, defoamingagents, processing aids, mica, talc, nano-fillers, antioxidants,stabilizers, softening agents, fragrance components, impact modifiers,TiO₂, acid copolymer wax, surfactants, and fillers, such as zinc oxide,tin oxide, barium sulfate, zinc sulfate, calcium oxide, calciumcarbonate, zinc carbonate, barium carbonate, clay, tungsten, tungstencarbide, silica, lead silicate, rubber core regrind (recycled material),and mixtures thereof.

The plasticized compositions of the present invention are not limited byany particular method or any particular equipment for making thecompositions. In a preferred embodiment, the composition is prepared bythe following process. The non-acid polymer(s) and plasticizers, andoptional additives/fillers are simultaneously or individually fed into amelt extruder, such as a single or twin screw extruder. Other suitablemethods for incorporating the plasticizer into the composition aredescribed further below. The components are intensively mixed prior tobeing extruded as a strand from the die-head. Additional methods forincorporating plasticizer into the thermoplastic compositions herein aredisclosed in co-pending, co-assigned U.S. patent application Ser. No.13/929,841, as well as in U.S. Pat. Nos. 8,523,708 and 8,523,709, whichare fully incorporated by reference herein.

It is believed that adding the plasticizer to the non-acid polymer helpsmake the composition softer and more rubbery. Adding the plasticizers tothe composition helps decrease the stiffness of the composition. Thatis, the plasticizer helps lower the flex modulus of the composition. Theflex modulus refers to the ratio of stress to strain within the elasticlimit (when measured in the flexural mode) and is similar to tensilemodulus. This property is used to indicate the bending stiffness of amaterial. The flexural modulus, which is a modulus of elasticity, isdetermined by calculating the slope of the linear portion of thestress-strain curve during the bending test. If the slope of thestress-strain curve is relatively steep, the material has a relativelyhigh flexural modulus meaning the material resists deformation. Thematerial is more rigid. If the slope is relatively flat, the materialhas a relatively low flexural modulus meaning the material is moreeasily deformed. The material is more flexible. The flex modulus can bedetermined in accordance with ASTM D790 standard among other testingprocedures. Thus, in one embodiment, the first non-acid copolymer(containing non-acid polymer only) composition has a first flex modulusvalue and the second non-acid polymer (containing non-acid polymer andplasticizer) composition has a second flex modulus value, wherein thesecond flex modulus value is at least 1% less; or at least 2% less; orat least 4% less; or at least 8% less; or at least 10% less than thefirst modulus value.

More particularly, in one embodiment, the non-acid polymer/plasticizercomposition has a flex modulus lower limit of about 500 (or less),1,000, 1,600, 2,000, 4,200, 7,500, 9,000, 10,000 or 20,000 or 40,000 or50,000 or 60,000 or 70,000 or 80,000 or 90,000 or 100,000; and a flexmodulus upper limit of about 110,000 or 120,000 or 130,000 psi or140,000 or 160,000 or 180,000 or 200,000 or 300,000 or greater. Ingeneral, the properties of flex modulus and hardness are related,whereby flex modulus measures the material's resistance to bending, andhardness measures the material's resistance to indentation. In general,as the flex modulus of the material increases, the hardness of thematerial also increases. As discussed above, adding the plasticizer tothe non-acid polymer helps reduce the flex modulus of the compositionand it also helps reduce hardness to a certain degree. Thus, in oneembodiment, the non-acid copolymer/plasticizer composition is relativelysoft and having a hardness of no greater than 40 Shore D or no greaterthan 55 Shore C. For example, the Shore D hardness may be within a rangehaving a lower limit of 5 or 8 or 10 or 12 or 14 and an upper limit of28 or 30 or 32 or 34 or 35 or 38 or 40 Shore D. The Shore C hardness maybe within the range having a lower limit of 10 or 13 or 15 or 17 or 19and an upper limit of 44 or 46 or 48 or 50 or 53 or 55 Shore C. In otherembodiments, the non-acid polymer/plasticizer composition is moderatelysoft having a hardness of no greater than about 60 Shore D or no greaterthan 75 Shore C. For example, the Shore D hardness may be within a rangehaving a lower limit of 25, 28, 20, 32, 35, 36, 38, or 40, and an upperlimit of 42, 45, 48, 50, 54, 56, or 60. The Shore C hardness may bewithin the range of having a lower limit of 30, 33, 35, 37, 39, 41, or43, and an upper limit of 62, 64, 66, 68, 71, 73 or 75 Shore C. In yetother embodiments, the non-acid polymer/plasticizer composition ismoderately hard having a hardness no greater than 95 Shore D or nogreater than 99 C. For example, the Shore D hardness may be within therange having a lower limit of about 42, 44, 47, 51, 53, or 58 and anupper limit of about 60, 65, 72, 77, 80, 84, 91, or 95 Shore D. TheShore C hardness may be within the range having a lower limit of 57, 59,62, 66, or 72 and an upper limit of about 75, 78, 84, 87, 90, 93, 95,97, or 99 Shore C.

It also is believed that adding the plasticizer to the non-acid polymercomposition helps reduce the glass transition temperature (Tg) of thecomposition in many instances. Thus, in one embodiment, the firstnon-acid polymer (containing non-acid polymer only) composition has afirst Tg value and the second non-acid polymer (containing non-acidpolymer and plasticizer) composition has a second Tg value, wherein thesecond Tg value is at least 1 degree (1°) less; or at least 2° less; orat least 4° less; or at least 8°; or at least 10° less than the first Tgvalue. In other embodiments, the first Tg value and the second Tg valueare approximately the same.

In addition, introducing the specific plasticizers of this inventioninto the non-acid polymer composition generally helps to reduce thecompression and/or increase the COR of the composition (when molded intoa solid sphere and tested) versus a non-plasticized composition (whenmolded into a solid sphere and tested.) Plasticized non-acid polymercompositions typically show compression values lower, or at most equalto, non-plasticized compositions while the plasticized compositionsdisplay COR values that may be higher, or at the least equal to,non-plasticized compositions. This effect is surprising, because in manyconventional compositions, the COR of the composition increases as thecompression increases. In some instances plasticization of thecomposition might produce a slight reduction in the COR while at thesame time reducing the compression to a greater extent, therebyproviding an overall improvement to the compression/COR relationshipover the non-plasticized composition.

Thus, the samples made from plasticized compositions of this inventionmay show a greater absolute resiliency than samples made fromconventional materials at a given compression. Having this relativelyhigh resiliency is an advantageous feature. In general, a core withhigher resiliency will reach a higher velocity when struck by a golfclub and travel longer distances. The “feel” of the ball also isimportant and this generally refers to the sensation that a playerexperiences when striking the ball with the club. The feel of a ball isa difficult property to quantify. Most players prefer balls having asoft feel, because the player experience a more natural and comfortablesensation when their club face makes contact with these balls. The feelof the ball primarily depends upon the hardness and compression of theball.

Cover Structure

As noted above, the golf ball assembly generally comprises a core thatis enclosed with a protective cover. The ball may contain one or morecover layers. For example, a golf ball having a single-layered cover maybe made. In another version, a golf ball having a two-layered coverincluding inner and outer cover layers may be made. In yet anotherversion, a three-layered cover including inner, intermediate, and outercover layers may be made. The cover layers of this invention provide theball with a variety of advantageous mechanical and playing-performanceproperties as discussed further below. In general, the hardness andthickness of the different cover layers may vary depending upon thedesired ball construction. In addition, as discussed above, anintermediate layer may be disposed between the core and cover layers.The cover layers preferably have good impact durability, toughness, andwear-resistance. The non-acid polymer/plasticizer composition of thisinvention is used to form at least one of the cover layers.

In one preferred version, the golf ball includes a multi-layered covercomprising inner, intermediate, and outer cover layers, wherein at leastone of the layers is formed of the non-acid polymer/plasticizercomposition of this invention. Different ball constructions usingdifferent combinations of the non-acid polymer/plasticizer materials maybe made in accordance with this invention. For example, theseplasticized thermoplastic compositions may be used to construct coverassemblies having three layers as described in the following Table I.

TABLE I Examples of Three-Layered Cover Assemblies Inner CoverIntermediate Core Layer Outer Core Layer Plasticized Thermoplastic Non-Second Thermoplastic Material Third Thermoplastic Material Acid PolymerMaterial Second Thermoplastic Material Plasticized Thermoplastic Non-Third Thermoplastic Material Acid Polymer Material PlasticizedThermoplastic Non- Plasticized Thermoplastic Non- Second ThermoplasticMaterial Acid Polymer Material Acid Polymer Material SecondThermoplastic Material Third Thermoplastic Material PlasticizedThermoplastic Non- Acid Polymer Material Plasticized Thermoplastic Non-Second Thermoplastic Material Plasticized Thermoplastic Non- AcidPolymer Material Acid Polymer Material Second Thermoplastic MaterialPlasticized Thermoplastic Non- Plasticized Thermoplastic Non- AcidPolymer Material Acid Polymer Material Plasticized Thermoplastic Non-Plasticized Thermoplastic Non- Plasticized Thermoplastic Non- AcidPolymer Material Acid Polymer Material Acid Polymer Material

In the above examples, “second and third thermoplastic materials” areused to form one or more of the cover layers. These other thermoplasticmaterials may be non-acid or acid polymers. Also, the formulations ofthe second and third thermoplastic materials may be the same ordifferent, and these formulations may have the same or differenthardness values. It should be understood that the above-described coverassemblies are only representative examples and are not meant to limitthe invention. Other materials may be used to form the cover layers. Forexample, thermoset materials, as described below, may be used to formany of the cover layers. Likewise, when more than one thermoset layer isused in the golf ball, the thermoset composition in the respectivelayers may be the same or different, and the composition may have thesame or different hardness values. In particularly preferred versions,the inner and/or intermediate cover layer is formed from the plasticizedthermoplastic composition of this invention, and the outer cover layeris formed from a suitable thermoset or thermoplastic composition.

Suitable “second and third thermoplastic materials” that can be used toform the cover layers include, but are not limited to, polyurethanes;polyureas; copolymers, blends and hybrids of polyurethane and polyurea;olefin-based copolymer ionomer resins (for example, Surlyn® ionomerresins and DuPont HPF® 1000, HPF® 2000, and HPF® 1035; and HPF® AD 1172,commercially available from DuPont; Iotek® ionomers, commerciallyavailable from ExxonMobil Chemical Company; Amplify® 10 ionomers ofethylene acrylic acid copolymers, commercially available from The DowChemical Company; and Clarix® ionomer resins, commercially availablefrom A. Schulman Inc.); polyethylene, including, for example, lowdensity polyethylene, linear low density polyethylene, and high densitypolyethylene; polypropylene; rubber-toughened olefin polymers; acidcopolymers, for example, poly(meth)acrylic acid, which do not becomepart of an ionomeric copolymer; plastomers; flexomers;styrene/butadiene/styrene block copolymers;styrene/ethylene-butylene/styrene block copolymers; dynamicallyvulcanized elastomers; copolymers of ethylene and vinyl acetates;copolymers of ethylene and methyl acrylates; polyvinyl chloride resins;polyamides, poly(amide-ester) elastomers, and graft copolymers ofionomer and polyamide including, for example, Pebax® thermoplasticpolyether block amides, commercially available from Arkema Inc;cross-linked trans-polyisoprene and blends thereof; polyester-basedthermoplastic elastomers, such as Hytrel®, commercially available fromDuPont or RiteFlex®, commercially available from Ticona EngineeringPolymers; polyurethane-based thermoplastic elastomers, such asElastollan®, commercially available from BASF; synthetic or naturalvulcanized rubber; and combinations thereof. Castable polyurethanes,polyureas, and hybrids of polyurethanes-polyureas are particularlydesirable because these materials can be used to make a golf ball havinghigh resiliency and a soft feel. By the term, “hybrids of polyurethaneand polyurea,” it is meant to include copolymers and blends thereof.

Polyurethanes, polyureas, and blends, copolymers, and hybrids ofpolyurethane/polyurea are also particularly suitable. When used as theouter cover layer material, polyurethanes and polyureas can be thermosetor thermoplastic. Thermoset materials can be formed into golf balllayers by conventional casting or reaction injection molding techniques.Thermoplastic materials can be formed into golf ball layers byconventional compression or injection molding techniques.

In such instances, where the plasticized thermoplastic composition ofthis invention is used to form one or more cover layers, a compositioncomprising an ionomer or a blend of ionomers can be used to form theother cover layer(s). Preferred ionomers are salts of O/X- andO/X/Y-type acid copolymers, wherein O is an α-olefin, X is a C₃-C₈α,β-ethylenically unsaturated carboxylic acid, and Y is a softeningmonomer. O is preferably selected from ethylene and propylene. X ispreferably selected from methacrylic acid, acrylic acid, ethacrylicacid, crotonic acid, and itaconic acid. Methacrylic acid and acrylicacid are particularly preferred. Y is preferably selected from (meth)acrylate and alkyl (meth) acrylates wherein the alkyl groups have from 1to 8 carbon atoms, including, but not limited to, n-butyl (meth)acrylate, isobutyl (meth) acrylate, methyl (meth) acrylate, and ethyl(meth) acrylate. Preferably, 0 is α-olefin, X is a C₃-C₈α,β-ethylenically unsaturated carboxylic acid present in an amount of 1to 20 wt. %, based on total weight of the copolymer, and Y is anacrylate selected from alkyl acrylates and aryl acrylates present in anamount of 0 to 50 wt. %, based on total weight of the copolymer, whereingreater than 70% of the acid groups present in the composition areneutralized with a metal ion.

Preferred O/X and O/X/Y-type copolymers include, without limitation,ethylene acid copolymers, such as ethylene/(meth)acrylic acid,ethylene/(meth)acrylic acid/maleic anhydride, ethylene/(meth)acrylicacid/maleic acid mono-ester, ethylene/maleic acid, ethylene/maleic acidmono-ester, ethylene/(meth)acrylic acid/n-butyl (meth)acrylate,ethylene/(meth)acrylic acid/iso-butyl (meth)acrylate,ethylene/(meth)acrylic acid/methyl (meth)acrylate,ethylene/(meth)acrylic acid/ethyl (meth)acrylate terpolymers, and thelike. The term, “copolymer,” as used herein, includes polymers havingtwo types of monomers, those having three types of monomers, and thosehaving more than three types of monomers. Preferred a, β-ethylenicallyunsaturated mono- or dicarboxylic acids are (meth) acrylic acid,ethacrylic acid, maleic acid, crotonic acid, fumaric acid, itaconicacid. (Meth) acrylic acid is most preferred. As used herein, “(meth)acrylic acid” means methacrylic acid and/or acrylic acid. Likewise,“(meth) acrylate” means methacrylate and/or acrylate. The acid polymeris preferably neutralized to 70% or higher, including up to 100%, with asuitable cation source, such as metal cations and salts thereof, organicamine compounds, ammonium, and combinations thereof. Preferred cationsources are metal cations and salts thereof, wherein the metal ispreferably lithium, sodium, potassium, magnesium, calcium, barium, lead,tin, zinc, aluminum, manganese, nickel, chromium, copper, or acombination thereof. These highly-neutralized ionomers may be referredto as highly-neutralized polymers (HNPs). However, it is understood thatother acid copolymer compositions may be used in accordance with thepresent invention. For example, acid copolymer compositions having acidgroups that are neutralized from about 20% to about less than 70% may beused, and these materials may be referred to as partially-neutralizedionomers. For example, the partially-neutralized ionomers may have aneutralization level of about 30% to about 65%, and more particularlyabout 35% to 60%.

These acid copolymer ionomers help impart some hardness to the ball, andmay be used in any cover layer, particularly inner and intermediatecover layers. For example, a cover layer may be formed from acomposition comprising ethylene acid copolymer ionomers such as Surlyns®and Nucrels®, available from DuPont. A particularly suitable high acidionomer is Surlyn 8150® (DuPont). Surlyn 8150® is a copolymer ofethylene and methacrylic acid, having an acid content of 19 wt %, whichis 45% neutralized with sodium. In another particular embodiment, theinner cover layer is formed from a composition comprising a high acidionomer and a maleic anhydride-grafted non-ionomeric polymer. Aparticularly suitable maleic anhydride-grafted polymer is Fusabond 525D®(DuPont). Fusabond 525D® is a maleic anhydride-grafted,metallocene-catalyzed ethylene-butene copolymer having about 0.9 wt %maleic anhydride grafted onto the copolymer. A particularly preferredblend of high acid ionomer and maleic anhydride-grafted polymer is an 84wt %/16 wt % blend of Surlyn 8150® and Fusabond 525D®. Blends of highacid ionomers with maleic anhydride-grafted polymers are furtherdisclosed, for example, in U.S. Pat. Nos. 6,992,135 and 6,677,401, theentire disclosures of which are hereby incorporated herein by reference.

The cover layers also may be formed from a composition comprising a50/45/5 blend of Surlyn® 8940/Surlyn® 9650/Nucrel® 960, and, in aparticularly preferred embodiment, the composition has a materialhardness of from 80 to 85 Shore C. In yet another version, the coverlayer is formed from a composition comprising a 50/25/25 blend ofSurlyn® 8940/Surlyn® 9650/Surlyn® 9910, preferably having a materialhardness of about 90 Shore C. The cover layer also may be formed from acomposition comprising a 50/50 blend of Surlyn® 8940/Surlyn® 9650,preferably having a material hardness of about 86 Shore C. A compositioncomprising a 50/50 blend of Surlyn® 8940 and Surlyn® 7940 also may beused. Surlyn® 8940 is an E/MAA copolymer in which the MAA acid groupshave been partially neutralized with sodium ions. Surlyn® 9650 andSurlyn® 9910 are two different grades of E/MAA copolymer in which theMAA acid groups have been partially neutralized with zinc ions.

Nucrel® 960 is an E/MAA copolymer resin nominally made with 15 wt %methacrylic acid. Nucrel® 9-1 (a copolymer of ethylene with 23.5%n-butyl acrylate, and about 9% methacrylic acid that is unneutralized);Nucrel® 2940 (a copolymer of ethylene and about 19% methacrylic acidthat is unneutralized); Nucrel® 0403 (a copolymer of ethylene and about4% methacrylic acid that is unneutralized); and Nucrel® 960 (a copolymerof ethylene and about 15% methacrylic acid that is unneutralized) alsomay be used. Surlyn® 6320 (a copolymer of ethylene with 23.5% n-butylacrylate, and about 9% methacrylic acid that is about 50% neutralizedwith a magnesium cation source); Surlyn® 8150 (a copolymer of ethylenewith about 19% methacrylic acid that is about 45% neutralized with asodium cation source); Surlyn® 8320 (a copolymer of ethylene with 23.5%n-butyl acrylate, and about 9% methacrylic acid that is about 52%neutralized with a sodium cation source); and Surlyn® 9120 (a copolymerof ethylene with about 19% methacrylic acid that is about 36%neutralized with a zinc cation source); and Surlyn® 9320 (a copolymer ofethylene with 23.5% n-butyl acrylate, and about 9% methacrylic acid thatis about 41% neutralized with a zinc cation source) also may be used.Primacor® 3150, 3330, 59801, 5986, and 59901 acid copolymers,commercially available from The Dow Chemical Company also may be used.

In another embodiment, a three-layered cover is made, wherein theplasticized thermoplastic non-acid polymer composition of this inventionis used to form the inner and intermediate cover; and a 50%/50% byweight blend of Surlyn® 8940/7940 is used to form the outer cover layer.Preferably, the plasticized composition used to form the inner andintermediate cover layers contains about 10% to about 40% ethyl oleateor other suitable plasticizer. Suitable hardness ranges for the coverlayers are described below. Methods for measuring the hardness levels ofcover layers also are described further below.

The relationship between the various cover layers is important in theconstruction of the golf ball of this invention. For example, inEmbodiment A, the three-layered cover has an outer cover comprising apolyurethane, polyurea, hybrid, blend, or copolymer thereof.Alternatively, the outer cover may comprise a soft ionomer, athermoplastic polyether block amide, such as Pebax™, available fromArkema, Inc., or thermoplastic polyester elastomer such as Hytrel™,available from DuPont, but it most preferably made of a polyurethanecomposition. In embodiment A, the intermediate cover layer comprises theplasticized thermoplastic non-acid polymer composition of thisinvention; and the innermost cover layer comprises either a “hard” acidcopolymer ionomer or a polyamide. The hardness of the polyurethane outerlayer is no greater than 55 Shore D, more preferably less than or equalto 50 Shore D. The intermediate cover layer has a hardness of 20 to 60Shore D, and the inner cover layer has a hardness of greater than 60Shore D. In embodiment A, the hardness of the outer cover layer is lessthan the hardness of the intermediate cover layer, and the hardness ofthe intermediate cover layer is less than the hardness of the innercover layer. In other words, when considering the three cover layers inEmbodiment A, the inner cover layer is the hardest cover layer.

In Embodiment B, a three-layered cover having the same three layers(outer, intermediate, and inner) as described in Embodiment A isproduced. However, the hardness of the layers in Embodiment B isdifferent than the hardness of the layers in Embodiment A. Particularly,the hardness of the outer cover layer is greater than the hardness ofthe intermediate cover layer, and the hardness of the outer cover layerand intermediate cover layer is greater than the hardness of the innercover layer. In other words, when considering the three cover layers inEmbodiment B, the outer cover layer is the hardest cover layer. Theinner cover layer may comprise the plasticized thermoplastic non-acidpolymer composition of this invention; and the outer cover layer maycomprise a “hard” acid copolymer ionomer.

In Embodiment C, a three-layered cover (outer, intermediate, and inner)also is produced, but the hardness of the layers in Embodiment C isdifferent than the hardness of the layers in Embodiments A and B.Particularly, the hardness of the intermediate cover layer in EmbodimentC is greater than the hardness of the inner and outer cover layers. Forexample, the hardness of the polyurethane outer cover layer may be nogreater than 55 Shore D, more preferably less than or equal to 50 ShoreD. The intermediate cover layer may have a hardness greater than 60Shore D, and the inner cover layer may have a hardness in the range ofabout 20 to about 60 Shore D. In other words, when considering the threecover layers in Embodiment C, the intermediate cover layer is thehardest cover layer. The inner and/or outer cover layers may comprisethe plasticized thermoplastic non-acid polymer composition of thisinvention; and the intermediate cover layer may comprise a “hard” acidcopolymer ionomer.

In Embodiment D, the outer cover layer comprises a “hard” ionomer havinga hardness of at least 60 Shore D; and the intermediate and/or innercover layer comprises a relatively softer plasticized thermoplasticnon-acid polymer composition of this invention.

As discussed above, the golf ball of this invention includes amulti-layered cover comprising inner, intermediate, and outer coverlayers, wherein at least one of the layers is formed of the non-acidpolymer/plasticizer composition. The compositions of the respectivecover layers may vary as described in above Table I; and the hardness ofthe layers also may vary. For example, in a first embodiment, theplasticized thermoplastic composition of this invention is used to formthe inner cover layer, and the hardness of the inner cover is less thanthe hardness of the intermediate and outer cover layers. Meanwhile, theintermediate and outer cover layers may have the same or differenthardness levels. So the hardness relationship is: InnerCover_(hardness)<Intermediate Cover_(hardness)≤ or ≥OuterCover_(hardness). In a modified version, the hardness of the inner coveris less than the hardness of the intermediate cover and yet it isgreater than the hardness of the outer cover layer.

In a second embodiment, the plasticized thermoplastic composition isused to form the intermediate cover layer, and the hardness of theintermediate cover is less than the hardness of the inner and outercover layers. Meanwhile, the inner and outer cover layers may have thesame or different hardness levels. That is the inner cover layer mayhave a hardness equal to, or less or greater than the outer cover layer.So the hardness relationship is: Inner Cover_(hardness)>IntermediateCover_(hardness)<Outer Cover_(hardness). In a modified version, thehardness of the intermediate cover is less than the hardness of theinner cover and yet it is greater than the hardness of the outer coverlayer.

In a third embodiment, the plasticized thermoplastic composition is usedto form the inner and intermediate cover layers, and the hardness of theinner and intermediate cover layers is less than the hardness of theouter cover layer. The inner and intermediate cover layers may have thesame or different hardness levels. So the hardness relationship is:Inner Cover_(hardness)≤ or ≥Intermediate Cover_(hardness)<OuterCover_(hardness).

In a fourth embodiment, the plasticized thermoplastic composition isused to form the outer cover layer, and the hardness of the inner andintermediate cover layers is greater than the hardness of the outercover layer. The inner and intermediate cover layers may have the sameor different hardness levels. So the hardness relationship is: InnerCover_(hardness)≤ or ≥Intermediate Cover_(hardness)>OuterCover_(hardness).

In a fifth embodiment, the plasticized thermoplastic composition is usedto form the inner and outer cover layers, and the hardness of the innerand outer covers is less than the hardness of the intermediate coverlayer. The inner and outer cover layers may have the same or differenthardness levels. So the hardness relationship is: IntermediateCover_(hardness)>Inner Cover_(hardness)≤ or ≥Outer Cover_(hardness).

In a sixth embodiment, the plasticized thermoplastic composition is usedto form the intermediate and outer cover layers, and the hardness of theintermediate and outer covers is less than the hardness of the innercover layer. So the hardness relationship is: InnerCover_(hardness)>Intermediate Cover_(hardness)≤ or ≥OuterCover_(hardness).

In a seventh embodiment, the plasticized thermoplastic composition isused to form each of the cover layers and the hardness of the coverlayers may be the same or different. So the hardness relationship is:Inner Cover_(hardness)≤ or ≥Intermediate Cover_(hardness)≤ or ≥OuterCover_(hardness).

In one version, the inner cover layer hardness is about 15 Shore D orgreater, more preferably about 25 Shore D or greater, and mostpreferably about 35 Shore D or greater. For example, the inner coverlayer hardness may be in the range of about 15 to about 60 Shore D, andmore preferably about 27 to about 48 Shore D. In another version, theinner cover layer hardness is about 50 Shore D or greater, preferablyabout 55 Shore D or greater, and most preferably about 60 Shore D orgreater. For example, in one version, the inner cover has a Shore Dhardness of about 55 to about 90 Shore D, or about 82 to about 99 ShoreC. In another embodiment, the inner cover has a Shore D hardness ofabout 60 to about 78 Shore D, and in yet another version, the innercover has a Shore D hardness of about 64 to about 72 Shore D. Moreparticularly, in one example, the inner cover has a hardness of about 65Shore D or greater. The hardness of the inner cover layer is measuredper the methods described further below. In addition, the thickness ofthe inner cover layer is preferably about 0.015 inches to about 0.100inches, more preferably about 0.020 inches to about 0.080 inches, andmost preferably about 0.030 inches to about 0.050 inches. Typically, thethickness of the inner cover is about 0.035 or 0.040 or 0.045 inches.

Turning to the intermediate cover layer, this layer preferably has ahardness of 70 Shore D or less, or 65 Shore D or less, or 60 Shore D orless, or 55 Shore D or less. Preferably, the intermediate cover has aShore D hardness in the range of about 25 Shore D to about 60 Shore D,more preferably about 38 to about 50 Shore D. In other embodiments,however, the intermediate cover has a hardness of greater than 70 ShoreD, for example, 75 Shore D or greater. Also, the thickness of theintermediate cover layer can vary. For example, in one version, thethickness of the intermediate cover layer is preferably about 0.005inches to about 0.040 inches, more preferably about 0.010 inches toabout 0.035 inches, and most preferably about 0.015 inches to 0.030inches.

Concerning the outer cover layer, this layer may be relatively thin. Theouter cover preferably has a thickness within a range having a lowerlimit of 0.004 or 0.006 or 0.008 and an upper limit of 0.010 or 0.020 or0.030 or 0.040 inches. Preferably, the thickness of the outer cover isabout 0.016 inches or less, more preferably 0.008 inches or less. Theouter cover preferably has a material hardness of 80 Shore D or less, or70 Shore D or less, or 60 Shore D or less, or 55 Shore D or less, or 50Shore D or less, or 45 Shore D or less. In one example, the outer coverpreferably has a Shore D hardness in the range of about 50 to about 80,more preferably about 55 to about 75. In another example, the outercover preferably has a Shore D hardness in the range of about 10 toabout 70, more preferably about 15 to about 60. The hardness of theouter cover layer is measured per the methods described further below.

In one version, the outer cover layer has a hardness (as measured on theball) in the range of about 55 to about 80 Shore D, or about 82 to about99 Shore C, and this surface hardness is greater than the surfacehardness of any other layer in the golf ball. In one version, the outersurface hardness (as measured on the ball) of the inner cover layer isless than the outer surface hardness of the core, but it is greater thanthe geometric center hardness (material hardness) of the core. Forexample, the core may have an outer surface hardness in the range ofabout 85 to about 95 Shore C and the inner cover layer may have an outersurface hardness in the range of about 50 to about 80 Shore C and thegeometric center hardness (material hardness) of the core may be in therange of about 30 to about 70 Shore C.

The hardness of a cover layer may be measured on the surface or midpointof the given layer in a manner similar to measuring the hardness of acore layer as described further below. For example, the hardness of theinner cover layer may be measured at the surface or midpoint of thelayer. A midpoint hardness measurement is preferably made for the innerand intermediate cover layers. The midpoint hardness of a cover layer istaken at a point equidistant from the inner surface and outer surface ofthe layer to be measured. Once one or more cover or other ball layerssurround a layer of interest, the exact midpoint may be difficult todetermine, therefore, for the purposes of the present invention, themeasurement of “midpoint” hardness of a layer is taken within plus orminus 1 mm of the measured midpoint of the layer. A surface hardnessmeasurement is preferably made for the outer cover layer. In theseinstances, the hardness is measured on the outer surface (cover) of theball. Methods for measuring the hardness are described in detail belowunder “Test Methods.”

The compositions used to make any cover layer (for example, inner,intermediate, or outer cover layer) may contain a wide variety offillers and additives to impart specific properties to the ball. Forexample, relatively heavy-weight and light-weight metal fillers such as,particulate; powders; flakes; and fibers of copper, steel, brass,tungsten, titanium, aluminum, magnesium, molybdenum, cobalt, nickel,iron, lead, tin, zinc, barium, bismuth, bronze, silver, gold, andplatinum, and alloys and combinations thereof may be used to adjust thespecific gravity of the ball. Other additives and fillers include, butare not limited to, optical brighteners, coloring agents, fluorescentagents, whitening agents, UV absorbers, light stabilizers, surfactants,processing aids, antioxidants, stabilizers, softening agents, fragrancecomponents, plasticizers, impact modifiers, titanium dioxide, clay,mica, talc, glass flakes, milled glass, and mixtures thereof.

The different hardness and thickness levels of the cover layers providethe ball with high impact durability and cut-, shear- andtear-resistance levels. In addition, the multi-layered cover, incombination with the core layer, helps impart high resiliency to thegolf balls. Preferably, the golf ball has a Coefficient of Restitution(CoR) of at least 0.750 and more preferably at least 0.800 (as measuredper the test methods below.) The core of the golf ball generally has acompression in the range of about 20 to about 130 and more preferably inthe range of about 60 to about 110 (as measured per the test methodsbelow.) These properties allow players to generate greater ball velocityoff the tee and achieve greater distance with their drives. At the sametime, the cover layers provide a player with a more comfortable andnatural feeling when striking the ball with a club. The ball is moreplayable and the ball's flight path can be controlled more easily. Otherball constructions, wherein the ball has a lower compression aredescribed further below.

More particularly, when sample spheres of the plasticized thermoplasticcomposition of this invention, which can be used to form the inner coverlayer, are prepared (1.55″ injection-molded spheres aged two weeks at23° C./50% RH), the samples preferably have a CoR of about 0.400 toabout 0.850 and a compression of about negative 250 to about 50. Incontrast when the ethylene acid copolymer ionomer blend (50/50 wt. %Surlyn 8940/7940), which can be used to form the outer cover layer, isinjection-molded into spheres, the samples preferably have a CoR ofabout 0.725 to about 0.820 and a compression of about negative 80 toabout 180.

Referring to FIG. 1, a perspective view of a finished golf ball that canbe made in accordance with this invention is generally indicated at(10). The dimples (12) may have various shapes and be arranged invarious patterns to modify the aerodynamic properties of the ball. InFIG. 2, a four-piece golf ball (14) with a multi-layered cover (16)comprising inner cover layer (16a), intermediate cover layer (16b), andouter cover layer (16c) is shown. The ball (14) further includes asolid, one-piece core (18). Turning to FIG. 3, the five-piece ball (20)includes a dual-core (22) comprising an inner core (center) (22a) andsurrounding outer core layer (22b). The multi-layered cover (26)encapsulates the core structure (22) and includes inner (26a),intermediate (26b), and outer (26c) cover layers. Finally, in FIG. 4, asix-piece ball (30) containing a dual-core (32) comprising inner (32a)and outer core layers (32b) is shown. An intermediate layer (34) isdisposed between the core structure (32) and multi-layered cover (36).The intermediate layer (34) also may be referred to as a casing layer.The intermediate layer (34) preferably has good water vapor barrierproperties to prevent moisture from penetrating into the core material.The ball may include one or more intermediate layers (34) disposedbetween the core (32) and cover (36) structures. The multi-layered cover(36) includes inner (36a), intermediate (36b), and outer (36c) coverlayers. Preferably, the inner cover and/or intermediate cover is made ofthe plasticized non-acid polymer composition.

Different ball constructions can be made using the cover assembly ofthis invention as shown in FIGS. 1-4 discussed above. Such golf ballconstructions include, for example, two-piece, three-piece, four-piece,five-piece, and six-piece constructions. It should be understood thatthe golf balls shown in FIGS. 1-4 are for illustrative purposes only,and they are not meant to be restrictive. Other golf ball constructionscan be made in accordance with this invention.

Core Structure

The above-described cover layers are disposed about a core sub-assemblyto form the finished golf ball. Single-layer or multi-layer cores may bemade. For example, a two-layered core having an inner core (center) andsurrounding outer core layer may be made in accordance with thisinvention. In another example, a three-layered core having an inner coreand outer core layer, wherein an intermediate core layer is disposedbetween the inner and outer core layers may be made. The plasticizedthermoplastic compositions, which are described above as being suitablefor making cover layers, are also suitable for forming the core layers.Thermoset rubber compositions and non-plasticized thermoplasticcompositions also are suitable for making core layers in accordance withthis invention. Thermoplastic compositions comprising acid polymers asdescribed above also can be used to form the inner and/or outer corelayers.

In one embodiment, the inner core (center) comprises a thermoplasticmaterial, for example, the plasticized thermoplastic non-acidcomposition of this invention or an acid polymer such as a O/X- andO/X/Y-type acid copolymers, wherein O is an α-olefin, X is a C₃-C₈α,β-ethylenically unsaturated carboxylic acid, and Y is a softeningmonomer. 0 is preferably selected from ethylene and propylene. X ispreferably selected from methacrylic acid, acrylic acid, ethacrylicacid, crotonic acid, and itaconic acid. Methacrylic acid and acrylicacid are particularly preferred. Y is preferably selected from (meth)acrylate and alkyl (meth) acrylates wherein the alkyl groups have from 1to 8 carbon atoms, including, but not limited to, n-butyl (meth)acrylate, isobutyl (meth) acrylate, methyl (meth) acrylate, andethyl(meth) acrylate.

In another embodiment, the inner core comprises a thermoset material.Suitable thermoset materials that may be used to form the inner coreinclude, but are not limited to, polybutadiene, polyisoprene, ethylenepropylene rubber (“EPR”), ethylene-propylene-diene (“EPDM”) rubber,styrene-butadiene rubber, styrenic block copolymer rubbers (such as“SI”, “SIS”, “SB”, “SBS”, “SIBS”, and the like, where “S” is styrene,“I” is isobutylene, and “B” is butadiene), polyalkenamers such as, forexample, polyoctenamer, butyl rubber, halobutyl rubber, polystyreneelastomers, polyethylene elastomers, polyurethane elastomers, polyureaelastomers, metallocene-catalyzed elastomers and plastomers, copolymersof isobutylene and p-alkylstyrene, halogenated copolymers of isobutyleneand p-alkylstyrene, copolymers of butadiene with acrylonitrile,polychloroprene, alkyl acrylate rubber, chlorinated isoprene rubber,acrylonitrile chlorinated isoprene rubber, and blends of two or morethereof.

The thermoset rubber materials may be cured using a conventional curingprocess as described further below. Suitable curing processes include,for example, peroxide-curing, sulfur-curing, high-energy radiation, andcombinations thereof. Preferably, the rubber composition contains afree-radical initiator selected from organic peroxides, high energyradiation sources capable of generating free-radicals, and combinationsthereof. In one preferred version, the rubber composition isperoxide-cured. Suitable organic peroxides include, but are not limitedto, dicumyl peroxide; n-butyl-4,4-di(t-butylperoxy) valerate;1,1-di(t-butylperoxy)3,3,5-trimethylcyclohexane;2,5-dimethyl-2,5-di(t-butylperoxy) hexane; di-t-butyl peroxide;di-t-amyl peroxide; t-butyl peroxide; t-butyl cumyl peroxide;2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3;di(2-t-butyl-peroxyisopropyl)benzene; dilauroyl peroxide; dibenzoylperoxide; t-butyl hydroperoxide; and combinations thereof. In aparticular embodiment, the free radical initiator is dicumyl peroxide,including, but not limited to Perkadox® BC, commercially available fromAkzo Nobel. Peroxide free-radical initiators are generally present inthe rubber composition in an amount of at least 0.05 parts by weight per100 parts of the total rubber, or an amount within the range having alower limit of 0.05 parts or 0.1 parts or 1 part or 1.25 parts or 1.5parts or 2.5 parts or 5 parts by weight per 100 parts of the totalrubbers, and an upper limit of 2.5 parts or 3 parts or 5 parts or 6parts or 10 parts or 15 parts by weight per 100 parts of the totalrubber. Concentrations are in parts per hundred (phr) unless otherwiseindicated. As used herein, the term, “parts per hundred,” also known as“phr” or “pph” is defined as the number of parts by weight of aparticular component present in a mixture, relative to 100 parts byweight of the polymer component. Mathematically, this can be expressedas the weight of an ingredient divided by the total weight of thepolymer, multiplied by a factor of 100.

The rubber compositions may further include a reactive cross-linkingco-agent. Suitable co-agents include, but are not limited to, metalsalts of unsaturated carboxylic acids having from 3 to 8 carbon atoms;unsaturated vinyl compounds and polyfunctional monomers (e.g.,trimethylolpropane trimethacrylate); phenylene bismaleimide; andcombinations thereof. Particular examples of suitable metal saltsinclude, but are not limited to, one or more metal salts of acrylates,diacrylates, methacrylates, and dimethacrylates, wherein the metal isselected from magnesium, calcium, zinc, aluminum, lithium, and nickel.In a particular embodiment, the co-agent is selected from zinc salts ofacrylates, diacrylates, methacrylates, and dimethacrylates. In anotherparticular embodiment, the agent is zinc diacrylate (ZDA). When theco-agent is zinc diacrylate and/or zinc dimethacrylate, the co-agent istypically included in the rubber composition in an amount within therange having a lower limit of 1 or 5 or 10 or 15 or 19 or 20 parts byweight per 100 parts of the total rubber, and an upper limit of 24 or 25or 30 or 35 or 40 or 45 or 50 or 60 parts by weight per 100 parts of thebase rubber.

Radical scavengers such as a halogenated organosulfur, organicdisulfide, or inorganic disulfide compounds may be added to the rubbercomposition. These compounds also may function as “soft and fastagents.” As used herein, “soft and fast agent” means any compound or ablend thereof that is capable of making a core: 1) softer (having alower compression) at a constant “coefficient of restitution” (COR);and/or 2) faster (having a higher COR at equal compression), whencompared to a core equivalently prepared without a soft and fast agent.Preferred halogenated organosulfur compounds include, but are notlimited to, pentachlorothiophenol (PCTP) and salts of PCTP such as zincpentachlorothiophenol (ZnPCTP). Using PCTP and ZnPCTP in golf ball innercores helps produce softer and faster inner cores. The PCTP and ZnPCTPcompounds help increase the resiliency and the coefficient ofrestitution of the core. In a particular embodiment, the soft and fastagent is selected from ZnPCTP, PCTP, ditolyl disulfide, diphenyldisulfide, dixylyl disulfide, 2-nitroresorcinol, and combinationsthereof.

The rubber composition also may include filler(s) such as materialsselected from carbon black, nanoclays (e.g., Cloisite® and Nanofil®nanoclays, commercially available from Southern Clay Products, Inc., andNanomax® and Nanomer® nanoclays, commercially available from Nanocor,Inc.), talc (e.g., Luzenac HAR® high aspect ratio talcs, commerciallyavailable from Luzenac America, Inc.), glass (e.g., glass flake, milledglass, and microglass), mica and mica-based pigments (e.g., Iriodin®pearl luster pigments, commercially available from The Merck Group), andcombinations thereof. Metal fillers such as, for example, particulate;powders; flakes; and fibers of copper, steel, brass, tungsten, titanium,aluminum, magnesium, molybdenum, cobalt, nickel, iron, lead, tin, zinc,barium, bismuth, bronze, silver, gold, and platinum, and alloys andcombinations thereof also may be added to the rubber composition toadjust the specific gravity of the composition as needed.

In addition, the rubber compositions may include antioxidants to preventthe breakdown of the elastomers. Also, processing aids such as highmolecular weight organic acids and salts thereof may be added to thecomposition. Suitable organic acids are aliphatic organic acids,aromatic organic acids, saturated mono-functional organic acids,unsaturated monofunctional organic acids, multi-unsaturatedmono-functional organic acids, and dimerized derivatives thereof.Particular examples of suitable organic acids include, but are notlimited to, caproic acid, caprylic acid, capric acid, lauric acid,stearic acid, behenic acid, erucic acid, oleic acid, linoleic acid,myristic acid, benzoic acid, palmitic acid, phenylacetic acid,naphthalenoic acid, and dimerized derivatives thereof. The organic acidsare aliphatic, mono-functional (saturated, unsaturated, ormulti-unsaturated) organic acids. Salts of these organic acids may alsobe employed. The salts of organic acids include the salts of barium,lithium, sodium, zinc, bismuth, chromium, cobalt, copper, potassium,strontium, titanium, tungsten, magnesium, cesium, iron, nickel, silver,aluminum, tin, or calcium, salts of fatty acids, particularly stearic,behenic, erucic, oleic, linoelic or dimerized derivatives thereof. It ispreferred that the organic acids and salts of the present invention berelatively non-migratory (they do not bloom to the surface of thepolymer under ambient temperatures) and non-volatile (they do notvolatilize at temperatures required for melt-blending.) Otheringredients such as accelerators (for example, tetra methylthiuram),processing aids, dyes and pigments, wetting agents, surfactants,plasticizers, coloring agents, fluorescent agents, chemical blowing andfoaming agents, defoaming agents, stabilizers, softening agents, impactmodifiers, antiozonants, as well as other additives known in the art maybe added to the rubber composition.

Examples of commercially-available polybutadiene rubbers that can beused in accordance with this invention, include, but are not limited to,BR 01 and BR 1220, available from BST Elastomers of Bangkok, Thailand;SE BR 1220LA and SE BR1203, available from DOW Chemical Co of Midland,Mich.; BUDENE 1207, 1207s, 1208, and 1280 available from Goodyear, Incof Akron, Ohio; BR 01, 51 and 730, available from Japan Synthetic Rubber(JSR) of Tokyo, Japan; BUNA CB 21, CB 22, CB 23, CB 24, CB 25, CB 29MES, CB 60, CB Nd 60, CB 55 NF, CB 70 B, CB KA 8967, and CB 1221,available from Lanxess Corp. of Pittsburgh, Pa.; BR1208, available fromLG Chemical of Seoul, South Korea; UBEPOL BR130B, BR150, BR150B, BR150L,BR230, BR360L, BR710, and VCR617, available from UBE Industries, Ltd. ofTokyo, Japan; EUROPRENE NEOCIS BR 60, INTENE 60 AF and P30AF, andEUROPRENE BR HV80, available from Polimeri Europa of Rome, Italy; AFDENE50 and NEODENE BR40, BR45, BR50 and BR60, available from Karbochem (PTY)Ltd. of Bruma, South Africa; KBR 01, NdBr 40, NdBR-45, NdBr 60, KBR710S, KBR 710H, and KBR 750, available from Kumho Petrochemical Co.,Ltd. Of Seoul, South Korea; DIENE 55NF, 70AC, and 320 AC, available fromFirestone Polymers of Akron, Ohio.

The polybutadiene rubber is used in an amount of at least about 5% byweight based on total weight of composition and is generally present inan amount of about 5% to about 100%, or an amount within a range havinga lower limit of 5% or 10% or 20% or 30% or 40% or 50% and an upperlimit of 55% or 60% or 70% or 80% or 90% or 95% or 100%. Preferably, theconcentration of polybutadiene rubber is about 40 to about 95 weightpercent. If desirable, lesser amounts of other thermoset materials maybe incorporated into the base rubber. Such materials include the rubbersdiscussed above, for example, cis-polyisoprene, trans-polyisoprene,balata, polychloroprene, polynorbornene, polyoctenamer, polypentenamer,butyl rubber, EPR, EPDM, styrene-butadiene, and the like.

As discussed above, in one embodiment, the core has a dual-layeredstructure. For example, an inner core (center) comprising athermoplastic ethylene acid copolymer or thermoset rubber composition asdescribed above may be prepared. Meanwhile, the outer core layer, whichsurrounds the inner core, also may comprise a thermoplastic or thermosetcomposition. In another embodiment, the core has a three-layeredstructure comprising an inner core, intermediate core layer, and outercore layer. For example, the core may include an inner core comprisingthe plasticized thermoplastic composition of this invention; anintermediate core layer comprising a thermoplastic composition; and anouter core layer comprising a thermoset rubber composition.

Hardness of Core

The hardness of the core assembly (inner core and outer core layer) isan important property. In general, cores with relatively high hardnessvalues have higher compression and tend to have good durability andresiliency. However, some high compression balls are stiff and this mayhave a detrimental effect on shot control and placement. Thus, theoptimum balance of hardness in the core assembly needs to be attained.

In one preferred golf ball, the inner core (center) has a “positive”hardness gradient (that is, the outer surface of the inner core isharder than its geometric center); and the outer core layer has a“positive” hardness gradient (that is, the outer surface of the outercore layer is harder than the inner surface of the outer core layer.) Insuch cases where both the inner core and outer core layer each has a“positive” hardness gradient, the outer surface hardness of the outercore layer is preferably greater than the hardness of the geometriccenter of the inner core. In one preferred version, the positivehardness gradient of the inner core is in the range of about 2 to about40 Shore C units and even more preferably about 10 to about 25 Shore Cunits; while the positive hardness gradient of the outer core is in therange of about 2 to about 20 Shore C and even more preferably about 3 toabout 10 Shore C.

In an alternative version, the inner core may have a positive hardnessgradient; and the outer core layer may have a “zero” hardness gradient(that is, the hardness values of the outer surface of the outer corelayer and the inner surface of the outer core layer are substantiallythe same) or a “negative” hardness gradient (that is, the outer surfaceof the outer core layer is softer than the inner surface of the outercore layer.) For example, in one version, the inner core has a positivehardness gradient; and the outer core layer has a negative hardnessgradient in the range of about 2 to about 25 Shore C. In a secondalternative version, the inner core may have a zero or negative hardnessgradient; and the outer core layer may have a positive hardnessgradient. Still yet, in another embodiment, both the inner core andouter core layers have zero or negative hardness gradients.

In general, hardness gradients are further described in Bulpett et al.,U.S. Pat. Nos. 7,537,529 and 7,410,429, the disclosures of which arehereby incorporated by reference. Methods for measuring the hardness ofthe inner core and outer core layers along with other layers in the golfball and determining the hardness gradients of the various layers aredescribed in further detail below. The core layers have positive,negative, or zero hardness gradients defined by hardness measurementsmade at the outer surface of the inner core (or outer surface of theouter core layer) and radially inward towards the center of the innercore (or inner surface of the outer core layer). These measurements aremade typically at 2-mm increments as described in the test methodsbelow. In general, the hardness gradient is determined by subtractingthe hardness value at the innermost portion of the component beingmeasured (for example, the center of the inner core or inner surface ofthe outer core layer) from the hardness value at the outer surface ofthe component being measured (for example, the outer surface of theinner core or outer surface of the outer core layer).

Positive Hardness Gradient. For example, if the hardness value of theouter surface of the inner core is greater than the hardness value ofthe inner core's geometric center (that is, the inner core has a surfaceharder than its geometric center), the hardness gradient will be deemed“positive” (a larger number minus a smaller number equals a positivenumber.) For example, if the outer surface of the inner core has ahardness of 67 Shore C and the geometric center of the inner core has ahardness of 60 Shore C, then the inner core has a positive hardnessgradient of 7. Likewise, if the outer surface of the outer core layerhas a greater hardness value than the inner surface of the outer corelayer, the given outer core layer will be considered to have a positivehardness gradient.

Negative Hardness Gradient. On the other hand, if the hardness value ofthe outer surface of the inner core is less than the hardness value ofthe inner core's geometric center (that is, the inner core has a surfacesofter than its geometric center), the hardness gradient will be deemed“negative.” For example, if the outer surface of the inner core has ahardness of 68 Shore C and the geometric center of the inner core has ahardness of 70 Shore C, then the inner core has a negative hardnessgradient of 2. Likewise, if the outer surface of the outer core layerhas a lesser hardness value than the inner surface of the outer corelayer, the given outer core layer will be considered to have a negativehardness gradient.

Zero Hardness Gradient. In another example, if the hardness value of theouter surface of the inner core is substantially the same as thehardness value of the inner core's geometric center (that is, thesurface of the inner core has about the same hardness as the geometriccenter), the hardness gradient will be deemed “zero.” For example, ifthe outer surface of the inner core and the geometric center of theinner core each has a hardness of 65 Shore C, then the inner core has azero hardness gradient. Likewise, if the outer surface of the outer corelayer has a hardness value approximately the same as the inner surfaceof the outer core layer, the outer core layer will be considered to havea zero hardness gradient.

More particularly, the term, “positive hardness gradient” as used hereinmeans a hardness gradient of positive 3 Shore C or greater, preferably 7Shore C or greater, more preferably 10 Shore C, and even more preferably20 Shore C or greater. The term, “zero hardness gradient” as used hereinmeans a hardness gradient of less than 3 Shore C, preferably less than 1Shore C and may have a value of zero or negative 1 to negative 10 ShoreC. The term, “negative hardness gradient” as used herein means ahardness value of less than zero, for example, negative 3, negative 5,negative 7, negative 10, negative 15, or negative 20 or negative 25. Theterms, “zero hardness gradient” and “negative hardness gradient” may beused herein interchangeably to refer to hardness gradients of negative 1to negative 10.

The inner core preferably has a geometric center hardness(H_(inner core center)) of about 5 Shore D or greater. For example, the(H_(inner core center)) may be in the range of about 5 to about 88 ShoreD and more particularly within a range having a lower limit of about 5or 10 or 18 or 20 or 26 or 30 or 34 or 36 or 38 or 42 or 48 or 50 or 52Shore D and an upper limit of about 54 or 56 or 58 or 60 or 62 or 64 or68 or 70 or 74 or 76 or 80 or 82 or 84 or 88 Shore D. In anotherexample, the center hardness of the inner core (H_(inner core center)),as measured in Shore C units, is preferably about 10 Shore C or greater;for example, the H_(inner core center) may have a lower limit of about10 or 14 or 16 or 20 or 23 or 24 or 28 or 31 or 34 or 37 or 40 or 44Shore C and an upper limit of about 46 or 48 or 50 or 51 or 53 or 55 or58 or 61 or 62 or 65 or 68 or 71 or 74 or 76 or 78 or 79 or 80 or 84 or90 Shore C. Concerning the outer surface hardness of the inner core(H_(inner core surface)), this hardness is preferably about 12 Shore Dor greater; for example, the H_(inner core surface) may fall within arange having a lower limit of about 12 or 15 or 18 or 20 or 22 or 26 or30 or 34 or 36 or 38 or 42 or 48 or 50 or 52 Shore D and an upper limitof about 54 or 56 or 58 or 60 or 62 or 70 or 72 or 75 or 78 or 80 or 82or 84 or 86 or 90 Shore D. In one version, the outer surface hardness ofthe inner core (H_(inner core surface)), as measured in Shore C units,has a lower limit of about 13 or 15 or 18 or 20 or 22 or 24 or 27 or 28or 30 or 32 or 34 or 38 or 44 or 47 or 48 Shore C and an upper limit ofabout 50 or 54 or 56 or 61 or 65 or 66 or 68 or 70 or 73 or 76 or 78 or80 or 84 or 86 or 88 or 90 or 92 Shore C. In another version, thegeometric center hardness (H_(inner core center)) is in the range ofabout 10 Shore C to about 50 Shore C; and the outer surface hardness ofthe inner core (H_(inner core surface)) is in the range of about 5 ShoreC to about 50 Shore C.

Meanwhile, the intermediate core layer preferably has an outer surfacehardness (H_(outer surface of the Inter Core)) of about 30 Shore D orgreater, and more preferably within a range having a lower limit ofabout 30 or 35 or 40 or 42 or 44 or 46 or 48 or 50 or 52 or 54 or 56 or58 and an upper limit of about 60 or 62 or 64 or 70 or 74 or 78 or 80 or82 or 85 or 87 or 88 or 90 Shore D. The outer surface hardness of theintermediate core layer (H_(outer surface of the Inter Core)), asmeasured in Shore C units, preferably has a lower limit of about 30 or32 or 36 or 40 or 45 or 50 or 55 or 60 or 63 or 65 or 67 or 70 or 73 or75 or 76 or 78 Shore C, and an upper limit of about 78 or 80 or 85 or 87or 89 or 90 or 92 or 93 or 95 Shore C. While, the midpoint (or innersurface) hardness of the intermediate core(H_(midpoint of the Inter Core)) preferably is about 25 Shore D orgreater and more preferably is within a range having a lower limit ofabout 26 or 30 or 34 or 36 or 38 or 42 or 48 of 50 or 52 Shore D and anupper limit of about 54 or 56 or 58 or 60 or 62 Shore D. As measured inShore C units, the midpoint hardness of the intermediate core(H_(midpoint of the Inter Core)) preferably has a lower limit of about35 or 38 or 44 or 52 or 58 or 60 or 70 or 74 Shore C and an upper limitof about 76 or 78 or 80 or 84 or 86 or 88 or 90 or 92 or 96 Shore C.

On the other hand, the outer core layer preferably has an outer surfacehardness (H_(outer surface of OC)) of about 40 Shore D or greater, andmore preferably within a range having a lower limit of about 40 or 42 or44 or 46 or 48 or 50 or 52 and an upper limit of about 54 or 56 or 58 or60 or 62 or 64 or 70 or 74 or 78 or 80 or 82 or 85 or 87 or 88 or 90Shore D. The outer surface hardness of the outer core layer(H_(outer surface of OC)), as measured in Shore C units, preferably hasa lower limit of about 40 or 42 or 45 or 48 or 50 or 54 or 58 or 60 or63 or 65 or 67 or 70 or 72 or 73 or 76 Shore C, and an upper limit ofabout 78 or 80 or 84 or 87 or 88 or 89 or 90 or 92 or 95 Shore C. And,the inner surface of the outer core layer (H_(inner surface of OC)) ormidpoint hardness of the outer core layer (H_(midpoint of OC)),preferably has a hardness of about 40 Shore D or greater, and morepreferably within a range having a lower limit of about 40 or 42 or 44or 46 or 48 or 50 or 52 and an upper limit of about 54 or 56 or 58 or 60or 62 or 64 or 70 or 74 or 78 or 80 or 82 or 85 or 87 or 88 or 90 ShoreD. The inner surface hardness (H_(inner surface of OC)) or midpointhardness (H_(midpoint of OC)) of the outer core layer, as measured inShore C units, preferably has a lower limit of about 40 or 42 or 44 or45 or 47 or 50 or 52 or 54 or 55 or 58 or 60 or 63 or 65 or 67 or 70 or73 or 75 Shore C, and an upper limit of about 78 or 80 or 85 or 88 or 89or 90 or 92 or 95 Shore C.

The midpoint of a core or cover layer is taken at a point equidistantfrom the inner surface and outer surface of the layer to be measured,most typically an outer core layer or inner cover layer. Once one ormore core layers surround a layer of interest, the exact midpoint may bedifficult to determine, therefore, for the purposes of the presentinvention, the measurement of “midpoint” hardness of a layer is takenwithin plus or minus 1 mm of the measured midpoint of the layer.

In one embodiment, the outer surface hardness of the outer core layer(H_(outer surface of OC)), is less than the outer surface hardness(H_(inner core surface)) or midpoint hardness (H_(midpoint of OC)), ofthe inner core by at least 3 Shore C units and more preferably by atleast 5 Shore C.

In a second embodiment, the outer surface hardness of the outer corelayer (H_(outer surface of OC)), is greater than the outer surfacehardness (H_(inner core surface)) or midpoint hardness(H_(midpoint of OC)), of the inner core by at least 3 Shore C units andmore preferably by at least 5 Shore C.

As discussed above, the inner core may be formed from a thermoplasticcomposition such as ethylene acid copolymer ionomer or a thermosetcomposition such as polybutadiene rubber. The outer core layer also maybe formed from such thermoplastic or thermoset compositions.

The core structure also has a hardness gradient across the entire coreassembly. In one embodiment, the (H_(inner core center)) is in the rangeof about 10 Shore C to about 60 Shore C, preferably about 13 Shore C toabout 55 Shore C; and the (H_(outer surface of OC)) is in the range ofabout 65 to about 96 Shore C, preferably about 68 Shore C to about 94Shore C or about 75 Shore C to about 93 Shore C, to provide a positivehardness gradient across the core assembly. In another embodiment, thereis a zero or negative hardness gradient across the core assembly. Forexample, the center of the core (H_(inner core center)) may have ahardness gradient in the range of 20 to 90 Shore C; and the outersurface of the outer core may have a hardness gradient in the range of10 to 80 Shore C. The hardness gradient across the core assembly willvary based on several factors including, but not limited to, thedimensions of the inner core, intermediate core, and outer core layers.

The United States Golf Association (USGA) has established a maximumweight of 45.93 g (1.62 ounces) for golf balls. For play outside of USGArules, the golf balls can be heavier. Thus, in such outside of the USGAcases, the balls can have a weight greater than 1.62 ounces. In onepreferred embodiment, the weight of the multi-layered core is in therange of about 28 to about 38 grams. Also, golf balls made in accordancewith this invention can be of any size, although the USGA requires thatgolf balls used in competition have a diameter of at least 1.68 inches.For play outside of USGA, the golf balls can be of a smaller size. Thus,in such outside of the USGA cases, the balls can have a diameter size ofless than 1.68 inches. Normally, golf balls are manufactured inaccordance with USGA requirements and have a diameter in the range ofabout 1.68 to about 1.80 inches. As discussed above, the golf ballcontains a cover which may be multi-layered and in addition may containintermediate layers, and the thickness levels of these layers also mustbe considered. Thus, in general, the dual-layer core structure normallyhas an overall diameter within a range having a lower limit of about1.00 or 1.20 or 1.30 or 1.40 inches and an upper limit of about 1.58 or1.60 or 1.62 or 1.66 inches, and more preferably in the range of about1.3 to 1.65 inches. In one embodiment, the diameter of the core assemblyis in the range of about 1.45 to about 1.62 inches.

Manufacturing of Golf Balls

The inner core may be formed by any suitable technique includingcompression and injection molding methods. The outer core layer, whichsurrounds the inner core, is formed by molding compositions over theinner core. Compression or injection molding techniques may be used toform the other layers of the core assembly. Then, the cover layers areapplied over the core assembly. Prior to this step, the core structuremay be surface-treated to increase the adhesion between its outersurface and the next layer that will be applied over the core. Suchsurface-treatment may include mechanically or chemically-abrading theouter surface of the core. For example, the core may be subjected tocorona-discharge, plasma-treatment, silane-dipping, or other treatmentmethods known to those in the art.

The cover layers are formed over the core or ball assembly (the corestructure and any intermediate layers disposed about the core) using asuitable technique such as, for example, compression-molding,flip-molding, injection-molding, retractable pin injection-molding,reaction injection-molding (RIM), liquid injection-molding, casting,spraying, powder-coating, vacuum-forming, flow-coating, dipping,spin-coating, and the like. Preferably, each cover layer is separatelyformed over the ball sub-assembly. For example, an ethylene acidcopolymer ionomer composition may be injection-molded to producehalf-shells. Alternatively, the ionomer composition can be placed into acompression mold and molded under sufficient pressure, temperature, andtime to produce the hemispherical shells. The smooth-surfacedhemispherical shells are then placed around the core sub-assembly in acompression mold. Under sufficient heating and pressure, the shells fusetogether to form an inner cover layer that surrounds the sub-assembly.In another method, the ionomer composition is injection-molded directlyonto the core sub-assembly using retractable pin injection molding. Anouter cover layer comprising a polyurethane or polyurea composition overthe ball sub-assembly may be formed by using a casting process.

After the golf balls have been removed from the mold, they may besubjected to finishing steps such as flash-trimming, surface-treatment,marking, coating, and the like using techniques known in the art. Forexample, in traditional white-colored golf balls, the white-pigmentedcover may be surface-treated using a suitable method such as, forexample, corona, plasma, or ultraviolet (UV) light-treatment. Then,indicia such as trademarks, symbols, logos, letters, and the like may beprinted on the ball's cover using pad-printing, ink-jet printing,dye-sublimation, or other suitable printing methods. Clear surfacecoatings (for example, primer and top-coats), which may contain afluorescent whitening agent, are applied to the cover. The resultinggolf ball has a glossy and durable surface finish.

In another finishing process, the golf balls are painted with one ormore paint coatings. For example, white primer paint may be appliedfirst to the surface of the ball and then a white top-coat of paint maybe applied over the primer. Of course, the golf ball may be painted withother colors, for example, red, blue, orange, and yellow. As notedabove, markings such as trademarks and logos may be applied to thepainted cover of the golf ball. Finally, a clear surface coating may beapplied to the cover to provide a shiny appearance and protect any logosand other markings printed on the ball.

Other Ball Constructions

It should be understood that the golf ball constructions described aboveare for illustrative purposes only, and they are not meant to berestrictive. Other golf ball constructions can be made in accordancewith this invention.

For example, very low compression golf balls comprising at least onecore or cover layer made from the plasticized thermoplastic compositionof this invention may be manufactured. The golf ball preferably has acompression of less than 60, more preferably less than 50 and may bewithin a range of from about negative 60 to positive 55 DCM. Morepreferably, the DCM range is from about negative 20 to positive 40, andmay be from about zero to 35, and may be about 5, 10, 20 or 25, 30, 45or 50 DCM. The ball can be a one-piece ball comprising a single layer ofthe plasticized thermoplastic composition, or a two- or more piece ballwith one or more layers comprising the plasticized thermoplasticcomposition (for example, core layer, cover layer, and/or intermediatelayer). For example, a very low compression two-piece ball may comprisea core of a thermoset polybutadiene and cover of a plasticizedthermoplastic composition. A very low compression three-layer ball maycomprise an inner core of a thermoset polybutadiene, an inner cover of aplasticized thermoplastic composition, and an outer cover of an ionomeror polyurethane. A very low compression four-layer golf ball may beconstructed with an inner core layer and an outer core layer, bothcomprising a thermoset polybutadiene, an inner cover layer comprising aplasticized thermoplastic composition, and an outer cover layercomprising an ionomer or polyurethane.

Test Methods

Hardness. The center hardness of a core is obtained according to thefollowing procedure. The core is gently pressed into a hemisphericalholder having an internal diameter approximately slightly smaller thanthe diameter of the core, such that the core is held in place in thehemispherical portion of the holder while concurrently leaving thegeometric central plane of the core exposed. The core is secured in theholder by friction, such that it will not move during the cutting andgrinding steps, but the friction is not so excessive that distortion ofthe natural shape of the core would result. The core is secured suchthat the parting line of the core is roughly parallel to the top of theholder. The diameter of the core is measured 90 degrees to thisorientation prior to securing. A measurement is also made from thebottom of the holder to the top of the core to provide a reference pointfor future calculations. A rough cut is made slightly above the exposedgeometric center of the core using a band saw or other appropriatecutting tool, making sure that the core does not move in the holderduring this step. The remainder of the core, still in the holder, issecured to the base plate of a surface grinding machine. The exposed‘rough’ surface is ground to a smooth, flat surface, revealing thegeometric center of the core, which can be verified by measuring theheight from the bottom of the holder to the exposed surface of the core,making sure that exactly half of the original height of the core, asmeasured above, has been removed to within 0.004 inches. Leaving thecore in the holder, the center of the core is found with a center squareand carefully marked and the hardness is measured at the center markaccording to ASTM D-2240. Additional hardness measurements at anydistance from the center of the core can then be made by drawing a lineradially outward from the center mark, and measuring the hardness at anygiven distance along the line, typically in 2 mm increments from thecenter. The hardness at a particular distance from the center should bemeasured along at least two, preferably four, radial arms located 180°apart, or 90° apart, respectively, and then averaged. All hardnessmeasurements performed on a plane passing through the geometric centerare performed while the core is still in the holder and without havingdisturbed its orientation, such that the test surface is constantlyparallel to the bottom of the holder, and thus also parallel to theproperly aligned foot of the durometer.

The outer surface hardness of a golf ball layer is measured on theactual outer surface of the layer and is obtained from the average of anumber of measurements taken from opposing hemispheres, taking care toavoid making measurements on the parting line of the core or on surfacedefects, such as holes or protrusions. Hardness measurements are madepursuant to ASTM D-2240 “Indentation Hardness of Rubber and Plastic byMeans of a Durometer.” Because of the curved surface, care must be takento ensure that the golf ball or golf ball sub-assembly is centered underthe durometer indenter before a surface hardness reading is obtained. Acalibrated, digital durometer, capable of reading to 0.1 hardness unitsis used for the hardness measurements and is set to record the maximumhardness reading attained for each measurement. The digital durometermust be attached to, and its foot made parallel to, the base of anautomatic stand. The weight on the durometer and attack rate conforms toASTM D-2240.

In certain embodiments, a point or plurality of points measured alongthe “positive” or “negative” gradients may be above or below a line fitthrough the gradient and its outermost and innermost hardness values. Inan alternative preferred embodiment, the hardest point along aparticular steep “positive” or “negative” gradient may be higher thanthe value at the innermost portion of the inner core (the geometriccenter) or outer core layer (the inner surface)—as long as the outermostpoint (i.e., the outer surface of the inner core) is greater than (for“positive”) or lower than (for “negative”) the innermost point (i.e.,the geometric center of the inner core or the inner surface of the outercore layer), such that the “positive” and “negative” gradients remainintact.

As discussed above, the direction of the hardness gradient of a golfball layer is defined by the difference in hardness measurements takenat the outer and inner surfaces of a particular layer. The centerhardness of an inner core and hardness of the outer surface of an innercore in a single-core ball or outer core layer are readily determinedaccording to the test procedures provided above. The outer surface ofthe inner core layer (or other optional intermediate core layers) in adual-core ball are also readily determined according to the proceduresgiven herein for measuring the outer surface hardness of a golf balllayer, if the measurement is made prior to surrounding the layer with anadditional core layer. Once an additional core layer surrounds a layerof interest, the hardness of the inner and outer surfaces of any inneror intermediate layers can be difficult to determine. Therefore, forpurposes of the present invention, when the hardness of the inner orouter surface of a core layer is needed after the inner layer has beensurrounded with another core layer, the test procedure described abovefor measuring a point located 1 mm from an interface is used. Likewise,the midpoint of a core or cover layer is taken at a point equidistantfrom the inner surface and outer surface of the layer to be measured,for example an outer core layer or inner cover layer. Also, once one ormore core layers surround a layer of interest, the exact midpoint may bedifficult to determine, therefore, for the purposes of the presentinvention, the measurement of “midpoint” hardness of a layer is takenwithin plus or minus 1 mm of the measured midpoint of the layer.

Also, it should be understood that there is a fundamental differencebetween “material hardness” and “hardness as measured directly on a golfball.” For purposes of the present invention, material hardness ismeasured according to ASTM D2240 and generally involves measuring thehardness of a flat “slab” or “button” formed of the material. Surfacehardness as measured directly on a golf ball (or other sphericalsurface) typically results in a different hardness value. The differencein “surface hardness” and “material hardness” values is due to severalfactors including, but not limited to, ball construction (that is, coretype, number of cores and/or cover layers, and the like); ball (orsphere) diameter; and the material composition of adjacent layers. Italso should be understood that the two measurement techniques are notlinearly related and, therefore, one hardness value cannot easily becorrelated to the other. Shore hardness (for example, Shore C or Shore Dhardness) was measured according to the test method ASTM D-2240.

Compression. As disclosed in Jeff Dalton's Compression by Any OtherName, Science and Golf IV, Proceedings of the World Scientific Congressof Golf (Eric Thain ed., Routledge, 2002) (“J. Dalton”), severaldifferent methods can be used to measure compression, including Atticompression, Riehle compression, load/deflection measurements at avariety of fixed loads and offsets, and effective modulus. The DCM is anapparatus that applies a load to a core or ball and measures the numberof inches the core or ball is deflected at measured loads. Aload/deflection curve is generated that is fit to the Atti compressionscale that results in a number being generated that represents an Atticompression. The DCM does this via a load cell attached to the bottom ofa hydraulic cylinder that is triggered pneumatically at a fixed rate(typically about 1.0 ft/s) towards a stationary core. Attached to thecylinder is an LVDT that measures the distance the cylinder travelsduring the testing timeframe. A software-based logarithmic algorithmensures that measurements are not taken until at least five successiveincreases in load are detected during the initial phase of the test.

Coefficient of Restitution (“COR”). The COR is determined according to aknown procedure, wherein a golf ball or golf ball sub-assembly (forexample, a golf ball core) is fired from an air cannon at two givenvelocities and a velocity of 125 ft/s is used for the calculations.Ballistic light screens are located between the air cannon and steelplate at a fixed distance to measure ball velocity. As the ball travelstoward the steel plate, it activates each light screen and the ball'stime period at each light screen is measured. This provides an incomingtransit time period which is inversely proportional to the ball'sincoming velocity. The ball makes impact with the steel plate andrebounds so it passes again through the light screens. As the reboundingball activates each light screen, the ball's time period at each screenis measured. This provides an outgoing transit time period which isinversely proportional to the ball's outgoing velocity. The COR is thencalculated as the ratio of the ball's outgoing transit time period tothe ball's incoming transit time period(COR=V_(out)/V_(in)=T_(in)/T_(out)).

It is understood that the compositions and golf ball products describedand illustrated herein represent only some embodiments of the invention.It is appreciated by those skilled in the art that various changes andadditions can be made to compositions and products without departingfrom the spirit and scope of this invention. It is intended that allsuch embodiments be covered by the appended claims.

We claim:
 1. A golf ball, comprising: i) a core having at least one layer; ii) an inner cover layer disposed about the core and having a Shore D midpoint hardness in the range of about 45 to about 75; iii) an intermediate cover layer comprising a thermoplastic material, the inner cover layer being disposed about the core and having a Shore D midpoint hardness in the range of about 15 to about 60, the thermoplastic material comprising: a) a thermoplastic non-acid polymer; and b) a plasticizer, the plasticizer being an alkyl oleate selected from the group consisting of methyl oleate, ethyl oleate, propyl oleate, butyl oleate, and octyl oleate, and mixtures thereof; and iv) an outer cover layer disposed about the intermediate cover layer and having a Shore D surface hardness in the range of about 45 to about 75, and wherein the outer cover and inner cover layers each have a hardness greater than the hardness of the intermediate cover layer.
 2. The golf ball of claim 1, wherein the non-acid polymer is selected from the group consisting of fluoropolymers, polystyrenes, polyolefins, polyamides, polyesters, polyethers, polyurethanes, polyureas, polyvinyl chlorides, polyvinyl acetates, polyimides, and mixtures thereof.
 3. The golf ball of claim 1, wherein the non-acid polymer is a polyamide selected from the group consisting of polyamide 6; polyamide 6,6; polyamide 6,10; polyamide 6,12; polyamide 11; polyamide 12; polyamide 6,9; and polyamide 4,6, and copolymers and blends thereof.
 4. The golf ball of claim 1, wherein the non-acid polymer is selected from the group consisting of a polyether-amide block copolymer and a polyester-polyether block copolymer, and mixtures thereof.
 5. A golf ball, comprising: i) a core having at least one layer; ii) an inner cover layer disposed about the core and having a Shore D midpoint hardness in the range of about 45 to about 75; iii) an intermediate cover layer disposed about the inner cover layer and having a Shore D midpoint hardness in the range of about 45 to about 75; iv) an outer cover layer disposed about the intermediate cover layer and having a Shore D midpoint hardness in the range of about 15 to about 60, the thermoplastic material comprising: a) a thermoplastic non-acid polymer; and b) a plasticizer, the plasticizer being an alkyl oleate selected from the group consisting of methyl oleate, ethyl oleate, propyl oleate, butyl oleate, and octyl oleate, and mixtures thereof; wherein the inner and intermediate cover layers each have a hardness greater than the hardness of the outer cover layer.
 6. The golf ball of claim 5, wherein the non-acid polymer is selected from the group consisting of fluoropolymers, polystyrenes, polyolefins, polyamides, polyesters, polyethers, polyurethanes, polyureas, polyvinyl chlorides, polyvinyl acetates, polyimides, and mixtures thereof.
 7. The golf ball of claim 5, wherein the non-acid polymer is a polyamide selected from the group consisting of polyamide 6; polyamide 6,6; polyamide 6,10; polyamide 6,12; polyamide 11; polyamide 12; polyamide 6,9; and polyamide 4,6, and copolymers and blends thereof.
 8. The golf ball of claim 5, wherein the non-acid polymer is selected from the group consisting of a polyether-amide block copolymer and a polyester-polyether block copolymer, and mixtures thereof. 